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COPYRIGHT DEPOSITS 



ELECTRIC 
RAILWAY ENGINEERING 



ELECTRIC 



RAILWAY ENGINEERING 



BY 

C. FRANCIS HARDING, E. E. 

n 

PROFESSOR, ELECTRICAL ENGINEERING; DIRECTOR, ELECTRICAL LABORATORIES, PURDUE 

UNIVERSITY; ASSOCIATE AMERICAN INSTITUTE ELECTRICAL ENGINEERS; ASSO- 
CIATE AMERICAN ELECTRIC RAILWAY ASSOCIATION; MEMBER SOCIETY 
FOR PROMOTION OF ENGINEERING EDUCATION 



McGRAW-HILL BOOK COMPANY 

239 WEST 39TH STREET, NEW YORK 

6 BOUVERIE STREET, LONDON, E. C. 

1911 




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Copyright, 1911 

BY 

McGraw-Hill Book Company 



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Printed ajtd Electrotyped 

by The. Maple Press 

York, Pa* 



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PREFACE. 

To students in technical universities who wish to specialize 
in the subject of electrical railway engineering and to those who 
understand the fundamental principles of electrical engineering 
and are interested in their application to electric railway practice 
it is hoped that this book may be of value. 

While it is planned primarily for a senior elective course in a 
technical university, it does not involve higher mathematics 
and should therefore be easily understood by the undergraduate 
reader. 

The volume does not purport to present any great amount of 
new material nor principles, but it does gather in convenient form 
present day theory and practice in all important branches of 
electric railway engineering. 

No apology is deemed necessary for the frequent quotations from 
technical papers and publications in engineering periodicals, for it 
is only from the authorities and specialists in particular phases of 
the profession that the most valuable information can be obtained, 
and it is believed that a thorough and unprejudiced summary 
of the best that has been written upon the various aspects of the 
subject will be most welcome when thus combined into a single 
volume. 

The author wishes to express his appreciation of the assistance 
of Mr. Emrick, instructor in electrical engineering at Purdue 
University, in preparing illustrations for the book and to those 
students who by thesis investigations hav.e added to its value. 

LaFayette, Ind., September, 191 1. 



TABLE OF CONTENTS. 



PART I. 

Principles of Train Operation. 

I. History of Electric Traction 3 

11. Traffic Studies (predetermined) 13 

III. Traffic Studies (existing) 24 

IV. Train Schedules 30 

V. Motor Characteristics 35 

VI. Speed Time Curves (components) 48 

VII. Speed Time Curves (theory) 59 

VIII. Distance, Current and Power Time Curves (theory) 66 

IX. Speed, Distance, Current, and Power Curves (concrete examples) . 71 

X. Speed Time Curves (straight line) 78 

PART II. 

Power Generation and Distribution. 

I. Sub-station and Power Station Load Curves 87 

II. Distribution System 91 

III. Substation Location and Design 104 

IV. Transmission System 131 

V. Power House Location and Design 145 

VI. Bonds and Bonding 170 

VII. Electrolysis 178 

VIII. Signal and Dispatching Systems 188 

PART III. 

Equipment. 

I. Track Layout and Construction 205 

II. Rolling Stock 219 

HI. Motors 232 

IV. Types of Control 246 

V. Brakes 259 

VI. Car House Design 277 

VII. Electric Locomotives 288 

vii 



Vlll TABLE OF CONTENTS. 

PART IV. 

Types of Systems. 

I. Alternating Current vs. Direct Current Traction 305 

II. Electric Traction on Trunk Lines 319 



PART I. 

PRINCIPLES OF TRAIN OPERATION. 



CHAPTER I. 

. History of Electric Traction. 

Although it is not the purpose of this treatise to relate facts, but 
rather to study the engineering and economic problems en- 
countered in electric traction, yet it seems advisable to review 
briefly the history of the development of the electric railway by 
way of introduction. 

Two distinct epochs were encountered in the brief period in 
which electric traction has come to the front. The first was that 
in which the experimental designs were hardly more than models 
operated with primary batteries. Occasionally during this 
period, however, enthusiasts who did not realize the insuperable 
financial drawbacks of primary battery operation constructed and 
experimented with cars of considerable size operated in that 
manner. Such was the car constructed by Page in 185 1 for the 
Washington and Baltimore Railroad, which made use of a 16 
h. p. motor supplied with power from two large Grove cells made 
up of platinum plates 11 in. square. This first epoch was soon 
brought to a close, however, partly by the foresight of the inves- 
tigators who realized the limitations of the primary battery and 
partly by the failure of all attempts to commercialize the primary 
battery car by those who had continued to experiment therewith. 

The second epoch opened, after a brief interval of inactivity, 
simultaneously with the development of the reversible dynamo. 
In the development of this machine progressive experimenters 
could foresee the beginnings of electric traction upon a practical 
basis. Bearing in mind the existence of these two periods, the 
history of electric traction will be considered, greatly abstracted, 
but as nearly as possible in chronological order. 

Since electric traction has ever been dependent upon the elec- 
tric motor and the latter upon the discovery by Faraday, in 1821, 
that electricity could be made to produce mechanical motion, 
the latter date rather indirectly and vaguely marks the birth of 

3 



4 ELECTRIC RAILWAY ENGINEERING. 

the subject under consideration. America has the honor of first 
applying the electric motor to a car, model though it was, while 
later developments vibrated from America to Europe and back to 
America with a rapidity difficult to follow with accuracy. A poor 
blacksmith of Brandon, Vt., by the name of Thomas Davenport 
has the honor of first making this application of electric motor to a 
car in 1835, the motor having been constructed by him several 
years previous. During the short period of six years it is said that 
Davenport constructed over a hundred electric motors of various 
designs. That which was described as having been exhibited by 
him upon a car at Springfield and Boston, Mass., consisted of a 
revolving commutated magnet which was caused to attract sta- 
tionary armatures arranged around the periphery of its path of 
revolution. The car thus equipped was operated upon a small 
circular track. 

About the year 1838 Robert Davidson of Aberdeen, Scotland, 
built a much larger motor placed upon a battery car 16 ft. by 

5 ft. in dimensions of the gauge then standard and operated same 
with 40 cells of battery consisting of iron and amalgamated 
zinc plates immersed in dilute sulphuric acid. It is of interest 
to note -that after several successful trips over Scotland railways 
this car was purposely wrecked by steam railway engineers who 
were afraid it would supersede types in use at that time. 

Two rather fundamental patents were issued in England about 
this time, one in 1840 to Henry Pinkus involving the use of 
the rails for current conductors and another in 1855 to Swear 
which, although applied to telegraphic communication with 
moving trains, comprised the basis of the present current collect- 
ing trolley. Patents were also granted in 1855 by both France and 
Austria to Major Alexander Bessolo which covered the same 
fundamental principles but which described more in detail the 
third rail conductor, the insulated trolley, and even suggested 
central station supply. 

The experimental work in this country of Prof. Moses G. 
Farmer in 1847 and Thomas Hall in 1850 might be considered in 
particular because of the use for the first time of the rail as a con- 
ductor and the adoption of a geared speed reduction between 
motors and driving axle. The work of Page, previously men- 



HISTORY OF ELECTRIC TRACTION. 5 

tioned, deserves prominent mention at this time. For many 
years after these experiments investigations in electric traction 
seemed to be dormant, largely due to the general realization of 
the impracticability of the battery as a source of energy. 

The second era of electrical railway development opened about 
the year 1861 when Pacinotti invented the reversible continuous 
current dynamo. From this invention may be said to have arisen 
all modern generators and motors. While these were gradually 
developed by Gramme and Siemens, Wheatstone and Varley, 
Farmer and Rowland, Hefner-Alteneck and others, Wheatstone 
and Siemens having almost simultaneously developed self- 
exciting generators equipped with shunt and series winding, 
respectively, yet a considerable period of time elapsed before 
these developments were effectively applied to traction. 

The work of George F. Green, a poor mechanic of Kalamazoo, 
Mich., has been quoted as the connecting link between the two 
eras. Although he began his experiments as late at 1875, after 
the development of the dynamo, his first model road reverted to 
the battery delivering current to the car over the operating rails. 
Although Green proposed the trolley for his experimental track, 
he did not make use of it. The following work of this man is 
rather pathetic, in that he constructed a car about the year 1878 
large enough for two people and realized the advantages of the 
dynamo for supplying energy for same. He did not understand 
how to construct this machine himself, however, and was not 
financially able to procure one of the few being constructed 
abroad at that time. He applied, in 1879, for. patents which 
would probably have been of considerable value at that time, 
but because of limited funds and the fact that he was obliged to 
act as his own patent attorney, his claim was rejected and only 
finally granted in the year 1891 after a belated appeal to the cir- 
cuit court of the District of Columbia. 

The first electric road operating on a practical scale was the 
one exhibited by Siemens and Halske at the Berlin Exposition in 
1879. This consisted of an oval track about 1/3 mile in length 
upon which an electric locomotive was operated with three 
small trailers accommodating from 18 to 20 passengers. The 
motor was mounted with its axle lengthwise of the car and 



6 ■ ELECTRIC RAILWAY ENGINEERING. 

power was transmitted to the car axle through a double bevel 
gear speed reduction. A speed of about 8 miles per hour was 
attained. The current was supplied by means of a third rail 
located between the running rails. 

The year 1880 in Europe marked the exhibition of another 
model electric railway at Vienna by Egger which used the running 
rails for conductors. In this year also the study of a method of 
replacing the pneumatic dispatch system of Paris by miniature 
electrically propelled carriages was carried on. Siemens pro- 
posed at this time a commercial road for Berlin and endeavored 
to obtain a franchise for same. 

The first electric road to be installed apart from an exposition 
was that at Lichterfelde, near Berlin, which was opened in 1881. 
A single motor car using cable drive between motors and axles 
operated upon this road which was i i /2 miles in length, at a 
speed of about 30 miles per hour. It was sufficiently large to 
accomodate 36 passengers. Although a third rail road when 
installed, it was changed over 12 years later to a double trolley 
system. This road has remained in continuous operation. 
During this year, also, the horse railroad between Charlottenburg 
and Spandau was changed to electric traction. 

At the Paris exposition of 1881, Siemens and Halske demon- 
strated the use of the overhead trolley for current distribution 
to cars, the conductors consisting of metal tubes slotted on the 
underside, mounted upon wooden insulators; in which tubes, 
metal contactors, electrically connected with the car, were 
allowed to slide. In 1883, a 6-mile third rail road was opened at 
Portrush, Ireland, which was worthy of note because of its 
operation from a central station driven by water power. 

Referring back to this country, Thomas Edison and Stephen 
D. Field began experimenting about the year 1880. Edison was 
principally interested in the development of the incandescent and 
arc lamps at this time and aside from building a short road at 
his laboratory at Menlo Park and taking out a few patents, he did 
little in this line. Field did considerable pioneer work, having 
made plans in 1879 for a railway to be supplied with power by 
means of a conductor enclosed in a conduit and using the rails 
as a return circuit. In 1880-81 he constructed and put into 



HISTORY OF ELECTIRC TRACTION. 7 

operation an experimental electrical locomotive at Stockbridge, 
Mass. Patents were applied for by Field, Siemens, and Edison 
within 3 months of each other early in 1880. Since Field had 
filed a caveat, however, the year before, his papers were given 
priority. Field's plans, however, remained on paper until the 
latter part of the year 1880 which was a year later than the 
installation of the Berlin road. 

Little more was accomplished in the United States until 1883, 
when the interests of Edison and Field were united and the 
Electric Railway Company of the United States was organized. 
This company exhibited an electric locomotive at the Chicago 
Railway Exposition in 1883, which operated on a track about 
I /3 mile in length in the gallery of the exposition building. 
The motor operated a central driving shaft by means of bevel 
gears, this shaft being belted to one of the axles. The speed was 
varied by the use of resistances. Reverse motion was accom- 
plished by throwing into service an extra set of brushes by means 
of a lever, only one set of brushes, of course, being upon the com- 
mutator at any one time. 

Charles J. Van Depoele, a Belgian sculptor, who was destined 
to play an important part in the later development of electric 
traction, entered the field in 1882-83 when he operated a line in 
connection with the industrial Exposition at Chicago. After 
installing equipments at the New Orleans Exhibition and at 
Montgomery, Ala., and putting roads in operation at Windsor, 
Ont., Detroit, Mich., Appleton, Wis., and South Bend, Ind., the 
company which Van Depoele had formed was absorbed in 1888 
by the Thompson Houston Co., which had recently been organ- 
ized. The name of Leo Daft was one that cannot be neglected 
in the development of this period, for after considerable work 
with stationary motors in 1883 he constructed a locomotive 
capable of hauling a full sized car. The control in this car was 
brought about by varying the resistance of the motor field for 
which purpose some of the coils were wound with iron wire in 
place of copper. The company organized by Daft at Green- 
ville, N. J., installed roads at Coney Island, N. Y., and the 
Mechanic's Fair in Boston, and in 1885 equipped the Baltimore 
Union Passenger Ry. Co. with electric locomotives. During 



8 ELECTRIC RAILWAY ENGINEERING. 

this year electric traction was applied by this company to the 
Ninth Avenue lines in New York, but after a few experimental 
runs of the locomotive termed the "Benjamin Franklin" the 
experiment was abandoned. 

In 1884 Bentley and Knight installed a system in Cleveland, 
Ohio, which was probably the first to come into active competi- 
tion with a horse car line. Two miles of track were operated 
with under ground conductor in wooden slotted conduit. Motors 
were connected with car axles through the agency of wire cables. 

The railroad installed in Kansas City, Mo., in 1884, by J. C. 
Henry was noteworthy for its departure from other designs and 
its adoption of features which have since become standard prac- 
tice in electric railroading. Henry claims to have introduced the 
use of the overhead trolley. Whether this be true or not, the 
word "trolley" was first coined by the employees upon this road 
as a contraction for "troller" the word first applied to the four 
wheeled carriage which was used on the overhead wire as a 
current collector and connected with the car by means of a flexible 
cable. The use of the trolley rope for replacing the trolley was 
of much more significance than it would at first appear because 
of the fact that it was formerly customary to hire a boy to ride on 
top of the car to keep the trolley on the wire. The present system 
of span construction and feeder installation was first developed by 
Henry on this road. His overhead conductors consisted of two 
No. I B. & S. bare copper wires spliced every 60 ft., for this was 
the greatest single length procurable at this time. The rails 
used were those which had been installed 12 years before for 
horse car service and weighed but 12 lb. per yard. They were 
at first bonded by driving horse-shoe nails between the fish plates 
and the rails. The motor was a 5 h. p. Van Depoe e type con- 
nected with the axles by means of a clutch and a five speed differ- 
ential gearing. The generator was a series arc machine of 10 
h. p. developing a voltage up to 1000 volts. Although Henry 
was able to mount 7 per cent, grades without difficulty, the 
Cleveland road was the only other practical road operating in 
America at that time and it was extremely difficult to gain the 
confidence of the public. 

Of the roads that were installed during the next few years, 



HISTORY OF ELECTRIC TRACTION. 9 

the one which gave the greatest impetus to electric traction and 
the one often quoted as the first electric road in the United States 
was that in Richmond, Va., equipped in the year 1888 by Frank 
J. Sprague. At this time Mr. Sprague was already prominent 
in the railway field, although much of his time had been given 
to the development of the stationary motor. In a paper befoie 
the Society of Arts of Boston in 1885 he had advocated the equip- 
ment of the New York Elevated Railway with motors carried 
upon the trucks of the regular cars. In 1886 a series of tests 
were carried on upon the tracks of the 34th street branch of this 
road. These experiments, like many previous ones, however, 
were finally suspended because of the impossibility of interesting 
the railway management sufficiently to launch out upon a com- 
mercial installation. 

The motor design and suspension used by Sprague in these 
tests were the forerunners of present construction and therefore 
worthy of a brief description. The motor frame contained bear- 
ings mounted upon the car axle, thus permitting the former to 
swing slightly about the axle as a center keeping the gear and pin- 
ion always in mesh on rough track. The other side of the motor 
frame w^as hung from the truck frame by means of springs. 
Single reduction gearing was used. Two motors were used on 
each truck but they were open to the weather. The first designs 
were shunt wound but later types made use of a series compen- 
sating winding. Control was obtained by resistance in both 
armature and field circuits. The motors were used for returning 
energy to the line as well as for braking. 

Before considering further the rather important installation 
at Richmond, it is well to consider a census of electric traction 
development early in 1887. In Europe at this time there were 
but nine installations including but 20 miles of track taking into 
consideration every type of electric traction including that in 
mines. In the United States there were 10 such installations 
involving 40 miles of track and 50 motor cars. Public prejudice 
had not been overcome and no system of any size had been 
operated commercially. 

The Sprague Electric Railway and Motor Company, contracted 
for installations at St. Joseph, Mo., and Richmond, Va., during 



lO ELECTRIC RAILWAY ENGINEERING. 

the year 1887, the latter contract covering a complete new road 
including generating station, overhead lines, and the equipment 
of 40 motor cars with two 7 i /2 h. p. motors each. It was placed 
in operation in February, 1888, and many were the new experiences 
and amusing anecdotes connected with this installation. The 
distribution system consisted of an overhead conductor mounted 
over the center of the track with a second parallel conductor on 
the pole line supplied with feeders from the power station and 
extending to various distributing points. The power station 
was equipped with six 40 k. w. 500 volt Edison generators driven 
by three 125 h. p. engines. Upon each axle of the car was 
mounted an exposed motor in the manner previously described. 
The single reduction gearing employed at first was later re- 
placed by the double reduction type. The speed control was 
effected by two separate switches, one changing the field con- 
nections from series to parallel and the other making similar 
changes in the armature circuit. The cars could be operated in 
either direction from either end and the entire weight of the car 
was available for traction. Motors were operated in both direc- 
tions, at first with laminated brushes fixed at an angle and later 
with radial solid metallic brushes. The success of this road at 
Richmond, in the face of many reverses and new engineering 
problems which had to be overcome, was probably largely due to 
the fact that Mr. Sprague was the first man with a competent 
education to enter the field. With this technical training to- 
gether with his familiarity with the failures of other experiments 
and the development of the stationary motor with which he was 
closely allied, he was able to solve the many difficult problems 
which arose and place this road on a practical operating basis. 

From this date electric traction became firmly seated and its 
future development was rapid, the natural tendency being to- 
ward heavier equipment. After investigation of the Richmond 
system the West End Railway of Boston soon adopted electric 
traction. In 1890 the South London road was equipped with 
electric locomotives and three years later the Liverpool overhead 
electric railway was put in operation. Third rail trains of four 
motor cars, equipped with hand control, hauling three trail care 
were used at the Chicago World's Fair in 1893 and in 1896 the 



HISTORY OF ELECTRIC TRACTION. 



II 



Nantasket branch of the New York and New Haven Railway 
was electrified. September of the same year saw the Lake 
Street Elevated of Chicago begin electrical operations and two 
months later electric service was begun on the Brooklyn Bridge. 
Since it is impossible to further list the new electric roads 
coming into existence the following table will be of value in point- 
ing out the remarkable growth of the electric railway in the 
United States. 

TABLE I. 
Growth of Electric Traction in United States. 



Year. 


No. 


electric roads. 


Miles track. 


1889 




50 


100 


1890 




200 


1200 


1891 




275 


2250 


1894 




606 


7470 


1895 (July) 




880 


10863 


1902 




739 


22000 



Note. — The decrease in the number of companies from 1895 to 1902 is probably 
due to the large amount of consolidation going on during this period. 

The most important changes in motor design that came with 
this progressive movement of the electric railway were the en- 
closing of the frame to protect the motor from the weather, the 
replacing of cast iron by steel, the change from two to four poles, 
the use of form wound coils and carbon brushes and the return to 
the old single gear reduction between motor and axle. The 
control system of 1892 made use of the combined resistance and 
series parallel connection, which is recognized as good practice 
to-day while the introduction of the blow out magnet was a long 
step forward in controller design. 

The more recent developments in electric traction comprise 
the use of alternating current for transmission to substations, 
the multiple unit control of the various cars of a train from a 
single master controller, the use of alternating current motors 
on the car, the electrification of steam roads with the more power- 
ful electric locomotives, and the use of high voltage direct current 
system. These problems are of such a broad nature and so im- 



12 ELECTRIC RAILWAY ENGINEERING. 

portant in the study of modern practice that they will be taken 
up more in detail elsewhere. Suffice it to say, by way of 
historical comment, that the rapid introduction of interurban 
railways beginning about the year 1894, together with the advances 
made in transformer design by Stanley, in polyphase transmission 
by Ferraris and Tesla and in the synchronous converter by 
Bradley and others brought about the first of the above mentioned 
changes, i.e., the use of alternating current for transmission pur- 
poses. Probably the first proposal to use such a system with 
substations was the one made by B. J. Arnold in 1896 for an 
interurban road to run out of Chicago. Although this particular 
line was not built, a similar system was installed about two years 
later. The multiple unit system was developed by F. J. Sprague 
who proposed its application to the New York Elevated Railway 
in 1896. After several vain endeavors to secure its adoption it 
was finally installed the following year by the South Side Elevated 
Railroad of Chicago and is now in common use on elevated sys- 
tems and is used to some extent in interurban traction. 

Summarizing briefly, the most prominent names in the develop- 
ment of the electric railway are found to be those of Faraday, 
Davenport, Farmer, Hall, Pacinotti, Siemens, Green, Field, Van 
Depoele, Daft, Bentley, Knight, Henry, and Sprague. While 
gradual developments have been going on more or less irregularly 
since 1835, the practical electric railroad, operating upon a com- 
mercial scale, dates back to about the year 1888. Vast strides 
have taken place since that date, however, until at the present 
time electric traction is the recognized transportation system in 
practically all cities and towns. It has tied together the larger 
cities with facilities for rapid passenger transit and for the trans- 
portation of both express and freight. It has opened up the city 
markets for the farmer of the small town, and the country sub- 
urbs for the residences of the city business man. It has com- 
peted successfully with the steam roads on interurban lines; it 
has found a foot-hold in the city terminals of the former, and is at 
present being seriously considered and in some particular cases 
has been adopted and successfully tried out for trunk line ser\dce. 
Rightly has it been said that its growth is without a parallel in 
the history of American invention and industrial progress. 



CHAPTER II. 
Traffic Studies (Predetermined;. 

One of the first considerations in connection with the planning 
of a new railroad or of an extension to an old system, whether 
it be within the limits of a city or an interurban line, is the study 
of probable traffic. Upon such a study is based the predeter- 
mination of gross income, train schedules, and power station 
demand. The importance, therefore, of an accurate and de- 
tailed study of all the factors which may affect the traffic upon a 
given road need not be emphasized further. 

Population. — A study of the railway census will disclose the 
fact that there is a fairly dependable relation between passenger 
traffic and population for both urban and interurban railroads. 
In the latter case, of course, the population under consideration 
must be that of the two terminal cities and, in most cases, a 
portion of the intermediate population which may be considered 
as tributary to the line. The determination of this tributary 
population is rather difficult, being largely dependent for its 
accuracy upon the experience and judgment of the engineer. In 
general, however, it is usually taken as the population of a 
strip of territory from i 1/2 to 2 miles in width on either 
side of the proposed railroad and parallel thereto. The popu- 
lation of such a strip may be determined by actual canvass or it 
may be assumed that the township or county through which the 
road extends is evenly populated throughout the rural districts. 
If this be true, the tributary population may be found from the 
following proportion. 

Tributary population Area strip. 

Township population Area township 
The township population may be obtained from the census 

reports and the required areas scaled from a map of the territory 

in question. 

While it will be found advisable t.n make an analysis of the 

13 



14 



ELECTRIC RAILWAY ENGINEERING. 



relation between population and passenger traffic per year, 
mileage of track economically operated, gross income, etc., for 
the entire country, a table or series of curves covering such data 
obtained from the particular locality in which the proposed road 
is to be operated will be found of more value. The nearer the 
conditions of installation and operation of these roads approach 
those of the proposed road, the more dependable will be the 
results based thereon. 

A table giving data of value in predetermining the traffic and 
gross income for a proposed road is given herewith for cities of 
the middle west under 25,000 population. 



TABLE II. 
Electric Railway Statistics.^ 



City, 



Popula- 
tion. 



Total. 



No. passen- 
gers per unit 
population. 



Total. 



Miles track 

per 1000 

population. 



Alton, North Alton, Up- |, 17,487 

per Alton, 111. 

Cairo, 111 12,566 

Kankakee, Bradley, Bour- 15,708 

bonnais, 111. 

Vincennes, Ind 

Burlington, la 

Ashtabula, O 

Lima, O 

Tiffin, O 

Zanesville, O 



10,249 
23,201 
12,949 

21,723 
10,989 

23,538 



1,497.130 

870,838 
714,769 

450,000 
1,600,000 

999,857 
1,375,979 

482,000 
1,800,000 



69 

45 

43 
69 

77 
63 

43 
76, 



.6 


12.25 ; 


•3 


9.67 


•5 


12.78 1 


•9 


8.00 

1 


.0 


14 50 ! 


.2 


5-75 ! 


•3 


18.55 


•9 


7-33 


•5 


10.00 

i 



0.70 

0.77 
0.81 

0.78 

0.62 

0.44 

0.85 

0.67 
0.42 



Whereas such a table offers more opportunity for the correct 
comparison of traffic, etc., for an urban road or for extensions 
to such a system than for the predetermination of interurban 
traffic, yet the methods outlined may be used to advantage in 
interurban developments providing they are applied with con- 
servative judgment based upon successful interurban experience. 
As an example of such adaptation of data to interurban practice 
it should be noted that a different proportion of terminal popula- 
tion will be tributary to the traffic of the proposed road in each 

^ Taken from Railway Census, 1902. 



TRAFFIC STUDIES. 1 5 

case under consideration. In the case of the road being the 
first to enter a relatively small terminal city, a large portion of 
the population of the city will avail itself of the road, but if the 
road is the fifth or sixth to enter such a city, as Indianapolis or 
Chicago, a relatively small portion of the population of the termi- 
nal city can be counted upon for passenger traffic. It follows 
directly from this, therefore, that with a large terminal city, 
the earnings of the road per capita of terminal population will- 
be small and the earnings of a successful road per mile of track 
will be relatively large and vice versa. 

Growth in Population. — It is necessary, however, to know 
more than the present terminal and tributary population. The 
growth of both for several years to come must be predicted. In 
order to do this intelligently it is necessary to know the growth 
in the past not only, but to study the causes of any eccentricities 
in the growth curve. It is only after such a detailed study that 
the population curve may be accurately extended to determine 
the population to be expected forty or fifty years hence. 

Bion J. Arnold, consulting engineer of Chicago, in his "Re- 
port on the Chicago Transportation Problem," points out very 
clearly the fallacy of predicting the population for any consider- 
able term of years by any rate of growth which has existed in the 
past, if the law of "Yearly decrease in the rate of increase" be 
neglected. If, by way of illustration, we refer to the curve of 
Fig. I which represents the population of the city of Phila- 
delphia during a long term of years, we shall see at once that 
had the future population of that city been predicted in i860 
from the rate of increase during the previous decade, the result 
would have been far from the fact. As a matter of fact, the rate 
of increase in population of Philadelphia dropped in five years 
from 1^7, per cent, per annum to 9 . 7 per cent, and, in another 
five years, to 2 . 9 per cent. Although this marked change in the 
rate of increase of population is exceptional in the case of Phila- 
delphia, x\rnold found that in the cases of the eight largest cites 
of the world which he studied the average rate of increase in 
population is gradually decreasing. It is obvious, therefore, 
that even if the average rate of increase in population over a 
long term of years were applied to the future growth of a city. 



i6 



ELECTRIC RAILWAY ENGINEERING. 



the results would still be too high. As an illustration, the 
average rate of increase in Chicago from 1837 to 1902 was 8.6 
per cent, per annum, from 1892 to 1902 it was 4.9 per cent., and 
during the year 1902 it was 7.7 per cent. Beginning with the 
year 1900 and compounding the population at 5 per cent., the 
resulting value for the year 1952 would be 18,500,000, while an 8 



2,100,000 

1,950,000 

1,800,000 

1,650,000 

1,500,000 

1,350,000 

1,200,000 

1,050,000 

900,000 

750,000 

600,000 

450,000 

300,000 

150,000 



































































POPULATION 

OF CITY OF 

PHILADELPHIA 

1800-1900 




























































J 






































/ / 




















'a 
















f77 



















'/ 


f 












^ 




/ 

yTA 


/ 
















y 


/ 
/ 










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'^.I'ic 


3 


i 


2^^ 











Fig. I. 



per cent, increase, compounded, would give this city a population 
of 26,500,000 in only 35 years. With the use of the more correct 
method, however, which takes into consideration the fact that 
the rate of increase is continually on the decline, the population is 
compounded with a constantly decreasing percentage. Such a 
method applied to the city of Chicago and beginning with the 1902 



TRAFFIC STUDIES. 



17 



rate of 7 per cent, results in a predicted population of 13,250,000 
for the year 1952. It is probable that this will mark the upper 
limit of the actual population curve, while the minimum limit 
of the area within which the population will fall in the next fifty 
years will be determined by a similar method of reasoning begin- 
ning with an increase rate of 3 per cent, w^hich represents the 



4,650,000 
4,500,000 

4,350,000 
4,300,000 
4,060,000 
3,900,000 
3,750,000 
3,000,000 
3,450,000 
3,300,000 
3,150,000 
3,000,000 
2,850,000 
2,700,000 





















1* 












i 

! 




// 






POPULATION OF 
CITY OF 
LONDON 
1861-1901 




m^ 










/ 








i 








ij 


1 
















^L 


li 
































i/i 


1 








j 

1 








r]^ 


I 1 

1 1 










1?f 










I 


S^l i 


















1 ; 
' 1 ■ 

! 1 
1 










/ 
















/ ^ 













Fig. 2. 



average growth of the large European cities. The result of the 
latter calculation gives Chicago a population of 5,250,000 in 1952. 
Reference to Figs. 2, 3, and 4 will give an idea of the changing 
rates of increase in population of the cities of London, Paris, and 
New York respectively. Several decades will be noted in these 
curves during which these rates have been abnormal; which rates. 



i8 



ELECTRIC RAILWAY ENGINEERING. 



if used as a basis for the predetermination of future population, 
would lead to very erroneous results. 

Riding Habit. — The proper determination of the "riding 
habit" for a given community or the number of passengers per 
capita of population per annum is important if the traffic of a 
proposed road is to be correctly predicted. This is always a 

2,700,000 
2,550,000 
2,400,000 
2,250,000 
2,100,000 
1,95.0,000 
1,800,000 
1.650,000 
1,500,000 
1,350,000 
1,250,000 
1,050,000 

900,000 

750,000 

600,000 

450,000 





















/ / 


















!A 


















-7 








POPULATION 

OF CITY OF 

PARIS 

1800-1900 




i 
1 

1 


/ 










11 
r 


8f. 
















f'j 


n 
(J 


















/t 


. 
















^/7 


















>^ 


i'/ 
^1 




















1/ 


■ 














-*'■/ 

4/'- 


li 














<^ 
















^^<i 


^01 

V 


^.r, 


: 












,i<^ 




















2.3?^ 





















Fig. 



local problem, dependent upon the geographical and industrial 
features of the country or city under consideration, as well as 
upon the customs of the people, the existing or possible forms of 
recreation, etc. In the case of the interurban road Httle aid 
can be obtained from tabulated results upon other roads for 
the possibility of comparison with a road where the conditions 



TRAFFIC STUDIES, 



19 



outlined above are the same is very small. For urban roads, 
however, reference may well be made to a curve (Fig. 5), plotted 
between ''passengers per capita per annum" and population 
throughout the country. This curve has been shown by one 
author^ to rise from approximately seventy passengers per capita 



2,100,000 

1,950,000 
1,800,000 
1,650,000 



1,500,000 

1,350,000 

1,200,000 

1,050,000 

900,000 

7.50,000 

600,000 

450,000 

300,000 

150,000 













































POPULATION 
OF CITY OF 

NEW YORK 
1800-1890 










































.2.8, t_ 


















A' 


















// 
// 

7 
















A 




>^ 


















^ 


















■' 


1 










'^ 


//i 

/Am 












e! 


^ 

// 


// 
















>^ 


^5.1 
















^^ 


j^.3 


i 












"4.85^ 


-2.75^ 














y—{ r 


3 5 

c 


■H .- 


z> c 


1 \ 




1 \ 




s c 
c 

a 
H r 


? g 

H T— 1 



Fig, 4, 



per annum in cities of 15,000 population to a constant value of 
240 in cities of 1,000,000 inhabitants and over, although Arnold's 
results in Chicago show an increase from 150 to 182 passengers 
per capita per annum from 1891 to 1901. 

Competition. — The question of competition with steam roads 



' See "Electric Railways," Vol. II, by S. W. Ashe. 



20 



ELECTRIC RAILWAY ENGINEERING. 



is a vital one with most interurban and suburban railroads, 
whereas most urban systems are practically monopolies. 

If the proposed road is to parallel a steam line, it is usually 
advisable to make a study of the traffic conditions on such an 
existing line, either from authentic records or by actual counting 
of passengers on all trains in the various seasons of the year. 
Such records must be applied with great caution, however, for 
it has been found that a well equipped interurban line with fre- 
quent and high speed service often takes away much local traffic 



320 
200 
180 
160 
140 
120 
100 



<\ 60 



40 



90 



































, 




— 




— 


















































"^ 






















































,^ 


^ 


























































^ 


^ 




























































^ 






























































/ 






























































/ 






























































/ 
































































/ 
















RELATION OF ANNUAL PASSENGERS 
PER CAPITA TO POPULATION. 


















































































































































































/ 
































































/ 
































































/ 
































































/ 
































































1 






































































































































































































































































































































































































































































































— 












_ 










— 





500,000 



1,000,000 



1,500,000 



Population 
Fig. 5. 



from the parallel steam lines not only, but, in addition, creates a 
traffic of its own. In other words, if the public can make a 
trip at any time of the day desired; if the cars are clean, free from 
smoke and cinders, and comfortable, and if the time lost en route 
is a minimum, it has been found that many ride who would other- 
wise remain at home. It is difficult to obtain more than a very 
rough approximation, therefore, of future traffic from steam rail- 
road statistics. That preference is given to the electric road and 
that traffic is often greatly reduced on existing steam lines with 



TRAFFIC STUDIES. 21 

the advent of the electric interurban line is clearly shown by the 
figures on the following table. 

TABLE III. 

Traffic on Lake Shore and Michigan Southern Between Cleveland and 

Oberlin ^ 



Westbound. Eastbound. Total. 



Average per 
month. 



1895 104,426 98,588 203,014 ' 16,918 

1902... 46,328 45.433 91.761 7>647 

Gross Income. — After having studied all statistics and local 
conditions which may possibly have a bearing upon the future 
trafl&c of a proposed road and having approximated from such 
study, combined with the riding habit of the people, the total 
traffic that may be expected with its hourly, daily, and season 
wide fluctuations, it will be necessary to determine the gross in- 
come possible from such a road. This may be done either by 
applying the average fare paid per passenger to the above traffic 
figures, which total may be augmented in some cases by express, 
freight, and mail receipts; or a comparison may be made with 
other similar roads operating successfully in the same locality and 
under similar conditions. Such a comparison based upon units 
of gross income per capita of terminal or tributary population or 
per mile of track gives very satisfactory results, as will be seen 
from the following example. 

In determining the gross income for a proposed fifty mile 
electric interurban line in Texas, connecting cities of 34,000 and 
58,000 inhabitants, comparison was made with two other roads 
operating under similar conditions with the following results. 

One of these roads, in the same state, connected cities of 15,000 
population each with 16 miles of track, returning a gross income 
in 1905 of $3.48 per capita of terminal population, while the 
second road, 81 miles in length, connecting cities of 26,000 and 
52,000 population, earned a gross income of $8.45 per capita. 
Taking the more conservative value of S3. 48 from the former 

^ See "American Electric Railway Practice," by Herrick and Boynton, p. 4. 



2 2 ELECTRIC RAILWAY ENGINEERING. 

road as a basis, the minimum return from the new road should 
be approximately 92000 X S3. 48 or $321,000, • representing an 
earning of $6,420 per mile. This figure compares very favorably 
with the corresponding values of $8,160 and $6,540 per mile 
for the two roads previously referred to. 

In order to determine the^net income it would be possible, of 
course, to approximate the operating expenses, fixed charges, 
etc., in detail, and subtract them from the gross income. A fair 
average ratio of net to gross income is often taken, however, as 
45 per cent. This figure applied to this particular road shows a 
net income of $144,500 annually and therefore a possible operating 
expense of $176,500. 

Number and Capacity of Cars. — The determination of the 
number and therefore the necessary carrying capacity of cars is 
sometimes arrived at as follows •} 

A well conducted road may safely be assumed to earn twenty 
cents per car mile. The car mileage per year may therefore be 
roughly obtained by dividing the gross income by the factor (0.2) 
The number of car miles per hour are, of course, readily deduced 
from the above quotient by dividing by the hours of actual car 
operation per year. If, then, the average schedule speed is speci- 
fied by city ordinance or is decided upon by the railway officials, 
the number of cars may readily be determined from the equation 

Car miles per hour. 

Number of cars = — - — ~— r-. . 

Schedule speed m miles per hour. 

However, the above result can be more satisfactorily and correctly 
obtained in most cases from train schedules. The total traffic 
to be expected having been calculated as explained above, the 
headway or schedule speed of cars is usually readily decided upon 
with a view toward carrying this amount of traffic or in ordei to 
successfully meet the competition of parallel steam roads. The 
graphical train schedule sheet explained in detail in Chapter IV 
may then be plotted, whereupon the number of cars necessary to 
maintain the proposed schedule immediately becomes apparent. 
It would be possible, of course, to determine the seating capacity 
and size of cars to be purchased for a given road from the theo- 

' See " Electric Railways" by S. W. Ashe, p. i6, Vol. II. 



TRAFFIC STUDIES. 23 

retical calculation of the probable number of passengers per trip 
at various times of day and at various seasons of year but such 
calculations seldom, if ever, become controlling features in the 
purchase of cars for a given road. For interurban roads the size 
and capacity of cars have been very well standardized by custom, 
the increased traffic at times being handled by changes in schedule 
or by the operation of two or more cars together in a train on 
the same schedule. As will be seen in the following chapter, 
however, cars are seldom operated at their exact seating capacity 
and in spite of the fact that standing in cars on interurban trips 
becomes most tedious and oppressive and, granting the conclusions 
discussed more at length in the following pages that a consider- 
able percentage of passengers stand in cars by preference, yet 
it is a regrettable fact that the size and headway of cars on many 
roads, especially in cases of urban traffic, are determined with 
but little consideration of the ratio of seating capacity to pass- 
enger traffic. 



CHAPTER HI. 
Traffic Studies (Existing). 

The necessity of making a careful study of existing traffic upon 
urban, interurban, and even steam railroads for the purpose of 
comparison with the conditions of a proposed line and in order 
to intelligently predetermine the probable income from, and 
therefore the advisability of financing and building a new line, 
has already been set forth. Further than this, those responsible 
for the successful operation of present and future lines must 
continually study the condition and tendencies of traffic. Quot- 
ing from a recent editorial in the Street Railway Journal upon 
this point, ''The managers of city railway systems which do not 
embrace more than a half-dozen routes usually" feel that they 
know every detail of the traffic distribution so well that it is 
unnecessary to go to the trouble of preparing graphic records. 
The correctness of this point of view, however, is not proved by 
the experience of those who have had occasion to prepare traffic 
curves, even for cities of less than 40,000 population, as they 
have found that such curves will betray the riding peculiarities of 
the public much more clearly than a mere tabulation. From such 
a record, for example, it is easy to observe whether the passengers 
take kindly to short trip cars or neglect them in favor of through 
cars even when they do not ride to the end of the line. 

"Traffic curves, furthermore, are not only of value to the com- 
pany in making up its schedule, but are also an aid in its relations 
to the public. When a complaint is made about the service on a 
certain line, it is surely convenient to be able to prove graphically 
that in the course of the day's operation the number of seats 
furnished far exceed the passengers and that the schedules 
adopted are based strictly upon the amount of traffic which the line 
brings." 

While reports of traffic investigations have been made public 
from time to time, especially as the results of studies by consulting 

24 



TRAFFIC STUDIES. 25 

engineers in connection with proposed improvements to the rail- 
way system for the purpose of reducing congestion of trafhc by 
means of subways, elevated lines, rerouting of cars, introduction 
of prepayment cars, etc., yet little has been said regarding the 
best methods of making such detailed studies with any degree of 
accuracy. In fact the difficulty in obtaining accurate and de- 
pendable results has often been given as an excuse for not under- 
taking such a study. It is also true that where conditions of 
traflSc are most variable, and these difficulties, therefore, most 
pronounced, the need of such an investigation is usually greatest 
and, when undertaken, results in the greatest possible improve- 
ment in service. 

It has been found where these traffic studies have been success- 
fully made that it is necessary to obtain data entirely independent 
of the daily returns of employees and that these data should be 
obtained by a crew of technically trained observers who under- 
stand the significance of every reading taken. The average 
car employee, no matter how loyal and conscientious, usually 
not understanding the use to be made of the data collected and 
the relative accuracy with which the various readings should be 
taken, has been found unsatisfactory for this work. 

It is usually advisable to subdivide the city roughly into dis- 
tricts such as business, manufacturing, residence, etc., and then 
to make a detailed study of the riding habits of the people and 
the loading of the cars on a single route or division at a time. 
It will at once be observed that the day may readily be divided 
into several periods of peak load, usually four in number. One 
city whose traffic conditions were investigated recently by the 
Wisconsin State Commission was found to have its four periods 
of peak load extending from 6.00 to 9.00 A. M., 11.00 A. m. to 2.00 
p. M., 5.00 to 8.00 p. M., and from 10.00 to 11.00 p. m., respectively.^ 
The last was, of course, the theatre period and was therefore 
limited to a small district of the city. 

In studying the problem further, it is usually found that the 
public at large has a very well defined habit of travel which 
does not vary greatly from one end of the year to another. Pleas- 
ure seekers and shoppers, of course, are irregular in their move- 

^ Graduate Thesis, Purdue University, 1910, by R. W. Harris. 



26 ELECTRIC RAILWAY ENGINEERING. 

ments, but the majority of passengers will soon be found to follow 
a definite route in their traveling, not only, but certain classes 
may be depended upon to ride during certain periods of the day. 
The above mentioned residence districts of the city and the pass- 
engers as well may, therefore, be still further subdivided as 
follows : 

1. Business or professional. 

2. Clerk and shoppers. 

3. Laborers. 

With such classifications in mind, it is necessary that the 
inspectors ride over the route or division under investigation a 
number of times during all periods of the day and in all kinds of 
weather to note roughly the effects of time of day, weather, and 
all local conditions upon maximum traffic. Especial notice 
should be taken of the stops which are of most importance, i.e., 
those at which most passengers leave and board cars. 

After such preliminary study the number of inspectors neces- 
sary, the particular stops to be studied, data to be recorded, and 
the number of readings to be taken in the detailed investigation 
may be decided upon. These readings may be taken by in- 
spectors, provided with stop watches located at the principal 
stopping points; or, if the number of cars is not too great, an 
inspector may be assigned to each car on the route. In general 
the observations to be made at the most important stops are as 
follows : 

1 . Line (route) . 

2. Period of day. 

3. Exact time. 

4. Direction of car. 

5. Number of car. 

6. Total number of people on car. 

7. Number of people standing in front vestibule. 

8. Number of people standing in rear vestibule. 

9. Number of people getting off car. 

10. Number of people getting on car. 

11. Class of passengers. 

12. Conditions of vehicular traffic. 

13. Conditions of pedestrian traffic. 



TRAFFIC STUDIES. 



27 



With symbols to represent many of the above conditions upon 
data sheets carefully prepared in advance and with a little ex- 
perience on the part of the inspector, the above data have been 
found to be readily and accurately taken. In fact in the investi- 
gations above alluded to check observations, taken independently 
but at the same time and place, varied less than 5 per cent. This 
is sufficiently accurate for the determinations desired. 





























— i- ■■ 
1 




















































CAR DEMAND CURVES 










































































m- 


■ 


















y 




































70- 


















1 y 


/ 


\ 


































5-t 














/ 


y 


V 




\ 
















^r 



















P 60- 

a 



■ 












y 








\ 












/ 




i 






■"^ 


[\ 






























l 


s. 








A 


/ 




1 

1 


Co 


ufo 


rta 


jle^ 


^ Load 






£ 50 

n 40- 












/ 










\ 






/ 


/ 






1 








1 
1 


\ 








- 








/ 










1 






/ 


/ 








1 








I 


\ 








1 








/ 


/ 
















<. 










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1 




\ 






^ 30- 








/ 












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1 








1 




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. 




/ 


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x 


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/ 


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1 




' -V, 


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;io 1 2? 

1 1 
[ Mixed 1,; 2, 3 Class Res. 

A R r n F 


1 30 40 
1 Blocks 

I (10 Blocks = 1 Mile 

Dis 1 


i 50 ; 60 

1 1-Out 

1 .J-In 

J ii II 1/- 




-—,,, J >,\',, ,,,. ' ^ Retail Bi'q. ^ 

lyiiilll.,: . 1, ■ =^^ , |.,,, , ,', ,. i j,|< , 


T !■ r 

V 3"g-Dis.l ' 

j'-jj;; ;jiiTijirnTnl tt 


,^ - 


1—1 

. 3- 


3rd Class Res. Dis/ 
/ 


i 


^il ill 


A 



Fig. 6. 



The results of an extensive investigation carried on in this way 
in one of the large cities of the west are typified by the single 
example represented by Fig. 6, in which the shaded areas repre- 
sent the various districts served by the particular car line under 
consideration, while the ordinates of the upper curve represent the 
passengers on the car during the period of maximum traffic ex- 
tending from 5.00 to 8.00 p. M. The abscissae of both curves 
represent the distance in miles on either side of the center of the 
city, while the full lines and dotted lines of the upper curve 



28 



ELECTRIC RAILWAY ENGINEERING. 



represent out-going and in-coming cars, respectively. It will be 
readily seen that the traffic at this time of day is largely from the 
city outward, as would be expected. Another point of significance 
is the fact that out-going cars from G to A take on the greater 
portion of their passengers between G and E which is the retail 
business district of the division, and deposit them principally 
between C and A which is in the mixed residence district. These 
passengers may properly be classed therefore as ^'clerks and 
shoppers." On the other hand the cars running from G to K 



so 

c 

a 



8 40 



7 35 



6 30 



25 



4 20 



3 15 



2 10 



1 5 



































































































































































PASSENGERS STANDING BY PREFERENCE 


















































































































































































































































































B 






































































































































y 


y 


































































9- 


y 
































































y 


y 






























































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= 


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1-4 5-9 10-14 15-19 20-24 25-29 

Total Number of Passengers on Car 

Fig. 7. 



30-34 



35-39 40-42 



take on their passengers between G and H within the wholesale 
business and manufacturing districts and deposit them between 
I and K in the third class residence district. This leads us to 
classify this traffic as ''laborers." In a similar manner it is 
possible to determine from curves resulting from careful investi- 
gation the tendency and amount of traffic on each division at all 
times of day. 

In order to determine, however, whether or not sufficient cars 
of ample capacity are being supplied, the "comfortable load" 
per car must be decided upon. During such investigations in 
several of the larger cities it has been found that a considerable 



TRAFFIC STUDIES. 29 

number of the passengers on a car stand by preference. In Fig. 7, 
curves A and A' show the total and percentage increase respec- 
tively of passengers standing by preference as the number of 
passengers on the car increases in a city of 25,000 population, 
while curves B and B' show curves of similar tendency for a 
city of 330,000 in the Middle West. Referring to curve B and 
with the knowledge that the cars operated in this city will seat 
42 passengers, it will be noted that when the car is fully loaded, 
eight will, on the average, stand by preference. The comfortable 
load has therefore been taken as 50 passengers and the variation 
of the "car demand" curves of Fig. 6 above and below the 
"comfortable load" line indicates at once the quality of service 
being rendered. 

It cannot be reasonably expected by the public that sufficient 
cars shall be furnished to enable every one to have a seat at all 
times of day, for many of the peak loads come on so suddenly 
and often so unexpectedly that it would be impossible to have the 
necessary cars at the proper time and place if it were the policy 
of the company to accomodate the peak traffic with seats. Most 
progressive companies, however, endeavor to meet the just de- 
mands of the riding public and therefore should determine those 
demands from time to time by methods similar to those outlined 
above. 



CHAPTER IV. 
Train Schedules. 

Having studied in the two previous chapters the important 
elements underlying the determination of probable traffic on a 
new railway line or upon the extension to an old system, it becomes 
necessary to establish the train schedule. As has been previously 
inferred, this is often a question of judgment to be exercised by 
the executive head of the road in view of the necessity of meeting 
competition. That is to say, the engineer who plans the details of 
the train schedule is instructed to arrange for hourly or half 
hourly interurban service, as the case may be, or the headway ex- 
pressed in minutes or distance between cars in feet may be spec- 
ified in the urban system. In both types of system the limiting 
schedule speed is usually stipulated, often by the municipalities in- 
volved. The interurban system is usually limited to two or more 
different schedule speeds, the higher velocities being confined to 
operation over private right of way and the lower within city 
limits or upon particularly dangerous sections of track such as 
trestles, draw-bridges, and temporary construction. 

Whereas the hours of train arrival and departure are usually 
placed in the hands of the public in the form of time tables, 
the most convenient and common form for the study of these 
data by railway engineers is the graphical chart. Many factors 
entering into the proper construction and successful operation of 
a road are at once apparent from such a chart or graphical train 
schedule. This train schedule is often plotted with time of day 
.in hours and minutes as ordinates and distances expressed in miles 
as abscissae. It is convenient if the ordinates representing the 
hours be designated by heavy lines on the coordinate paper and 
if the hourly sections be subdivided into sixths or twelfths, repre- 
senting ten and five minute intervals respectively. Upon the 

30 



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City Limit ^^ 



Galveaton 



TRAIN SCHEDULES. 



31 



distance scale it is customary to designate the distance between 
stations and the location of any points of especial engineering 
interest along the line such as branch lines, railway crossings, 
city and township limits, etc. With the scales of coordinates 
thus determined, a series of slanting lines. Fig. 8, may be drawn 
to represent the progress of the train from station to station. 
The slope of these lines is, of course, dependent upon speed, the 
co-tangent of the angle which they make with the horizontal 
representing the schedule speed of the train. A chart made up of 
such straight lines representing each train leaving the terminals 
of the line in either direction is sufficiently accurate for a rough 
preliminary study of traffic possibilities, power requirements, 
and substation locations, but before exact time tables can be 
adjusted and meeting points determined, a very much more ac- 
curate and detailed graphical train schedule must be drawn. 
Such a schedule involving three different schedule speeds over the 
various sections of road as well at the representation of the time 
elapsed in making station stops, is shown in Fig. 9, which is the 
proposed train schedule for a 50.6 mile interurban line, planned 
to connect the cities of Galveston and Houston, Texas, within 
whose limits the schedule speed was confined to 10 m. p. h. It 
should be noted that speeds of 30 m. p. h. and 55 m. p. h. are 
adopted for portions of the private right of way, while one minute 
has' been allowed for the average station stop. Such a graphical 
schedule enables one to predetermine not only the number of 
cars necessary to maintain a given schedule and the position of 
those cars at any moment, but it locates the meeting points, 
which are designated by the crossing of the schedule lines, and, 
when used in conjunction with the power curves of the various 
cars, it aids in locating substations and in determining the average 
and maximum loads on substations and power station. Com- 
paring Figs. 8 and 9 it will be noticed that while the former has 
the same through schedule speed as the latter and while all con- 
siderations based upon the headway and the time of leaving and 
arrival at terminal cities taken from Fig. 8 are quite as accurate 
as those taken from the more detailed chart, Fig. 9, yet it is clear 
that nothing of value can be learned from the former regarding 
the meeting points nor the positions of trains at any moment. 



32 ELECTRIC RAILWAY ENGINEERING. 

Although local conditions will prevent any extensive com- 
parison of train schedules of different roads or even the schedules 
of the same road at different seasons of year, yet it is believed 
that the principal factors to be borne in mind in plotting schedules 
can best be outlined by a more detailed study of the particular 
schedule of Fig. 9. 

This schedule is one proposed for maximum summer traffic. 
It has not been tried out in actual operation, and it is quite 
probable that hourly headway in place of the half hourly train 
spacing will best meet the demand. It will be noted that the 
first trains in the morning leave both terminals simultaneously 
at 6.00 A. M., and make the run in one hour and forty-five minutes 

1 Till 1 r 50.6x60 

requirmg a through schedule speed of = 20 m. p. h. 

105 

Further reference to the schedule will show that of this total time 
only 43 minutes is spent on the private right of way where the 
maximum speed of 55 m. p. h. is possible. While all trains stop 
at all stations within the city limits, there are a number of flag 
stops between these limits which tend to make the operating 
schedule irregular but which for convenience in plotting can be 
represented fairly accurately by allowing three flag stops for 
each train between the Southern Pacific Railway crossing and 
that of the T. C. T. Co., at which crossings all trains are required 
to stop. 

The corresponding points of meeting as graphically deter- 
mined fall sufficiently close together to be provided for by the six 
sidings shown at B, C, D, E, F, G, which are approximately 
I mile in length. These could be materially shortened by vary- 
ing the running time slightly. The meeting places within the 
city limits are so numerous that a double track extending from 
6 to 7 miles out of the city terminals would seem advisable from 
this preliminary study. 

The time table below, which was taken from the graphical 
schedule represented by Fig. 9, will be self explanatory and a 
comparison of the table and chart will illustrate the advantages 
of the graphical method even if the time table were to be the only 
result obtained therefrom. 



9:3C 



9:00 



8:30 



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6:30 



6:00 



G 
Gab 



miEBURBAN TRAIN SCHEDULE (final) 




^ Tel. E d, 
City Limit 

So. Pa. Ry 



TRAIN SCHEDULES. 

TABLE IV. 
Time Table. 



33 



Stations. 



North. 



South. 



Galveston i6.oo'6.30 7 .00 7 .308.00117 .45'8 



7.087.398.098.38 



7.18 7.48 8.18 8. 49 



7-047 



6-557 
6.527 



Genoa \6 .39 

Webster '6.48 

League City 16. 527 .21 7 .52 8.22 8.52 

Dickinson 16.56 7 .25 7 .57 8.26 8.56 6.47 7 

LaMarque J7 .05,7 .3618.06 8.35 9.06 6.38 7 

Houston 7. 45|8. 15 8.4519.15 9.45 6.00 6 



•15:8 
-35j8 

.27I7 

•237 
.197 
.097 

•307 



45'9-i5'9 
058.34^9 
56J8.268 

52'8.238 
488.188 



338.09 
ooi7.3o 



•45 
■05 
•56 
•52 
-48 

•39 
.00 



It has been previously stated that one of the advantages of the 
modern interurban system in competition with steam roads is 
its ability, to transport the passenger to more nearly the exact 
point in a terminal city to which he wishes to go and often gives 
him transfer privileges upon the local railway system if necessary. 
When comparing, therefore, the graphical train schedule of the 
interurban line with that of the competing steam road, especially 
with regard to the relatively long time required by the former 
within the city limits, it is often advisable to add to the steam 
schedule the walking time from terminal station to a point repre- 
senting the average destination of the travelling public if such 
can be found. Such "walking schedule" lines added to the train 
schedule often bring out very striking facts in favor of the electric 
railway as a popular choice of means of transportation. 

The particular schedule taken for illustration is a relatively 
simple one. With the addition of limited and local service and 
possibly freight and mail trains, and, in some cases, the necessity 
of meeting the schedules of trunk or branch lines, the graphical 
chart often becomes rather complicated. The use of a large 
scale drawing, however, usually permits such a solution to be 
made with little difficulty. In fact such schedules have been very 
satisfactorily used with the varied types of service outlined above, 
but with the additional requirement that the train be made up 
of a varying number of cars controlled by the multiple unit system, 
the various cars being feeders to the trunk line from the branches 



34 ELECTRIC RAILWAY ENGINEERING. 

en route and being joined together at the junction stations, thus 
forming the trains to enter the terminal city. The trains leaving 
the terminal city would operate in the reverse order, dropping car 
after car to the various branches and having relatively few through 
cars from terminal to terminal. 



CHAPTER V. 
Motor Characteristics. 

It will be readily recognized that the ordinary operation of a 
car, whether it be from block to block in the city or for a 5 or lo 
mile run between stations on an interurban private right of way, 
may be subdivided into periods of acceleration, constant speed 
running, coasting deceleration, braking deceleration, and stop. 
The conditions of particular runs as to length, grades, curves, 
etc., may materially vary or even eliminate some of these periods, 
but if all problems of car operation are to be solved, a detailed 
study of each of these portions of the so-called " speed time curve " 
must be undertaken. 

The principal factors entering into the determination of such 
a curve will be given detailed consideration in the following order, 
the present chapter dealing only with the first two functions. 

Motor characteristics. 

Gear ratio. / 

Weight of car. 

Bearing and rolling friction. 

Air resistance. 

Rotative inertia of wheels and armatures. 

Grades. 

Curves. 

Brake friction. 

Motor Characteristics. — In studying the characteristics of 
motors, in order to determine those best fitted for traction service, 
it may be found convenient to classify all motors into the follow- 
ing types : 

Direct Current: 
Series, 
Shunt, 
Compound, 
Cumulative, 
Differential. 

3S 



36 ELECTRIC RAILWAY ENGINEERING. 

Alternating Current, Polyphase: 

Induction, 

Synchronous. 
Alternating Current, Single Phase : 

Series, 

Induction, 

Synchronous, 

Repulsion. 
If the speed characteristics of all these motors be compared, it 
will be found that with varying loads within the rating of the 
motor the synchronous motors, both single and polyphase, 
maintain constant speed, while all the other direct and alternating 
current motors with the exception of the series type operate at 
nearly constant speed, the speed falling off slightly, usually in 
accordance with a straight line law, as the load increases. The 
speed characteristics of the compound motor may be made to 
approximate those of either the series or shunt motors by varying 
the relative strength of the series and shunt fields respectively. 
Since with constant potential motors, particularly of the direct 
current type, the current input to the motor varies approximately 
with the load, the speed-current curves of Fig. 10 may be taken 
as typical of the three classes of motors designed for commercial 
service. It should be noted that all of these motors maintain a 
speed of 400 r. p. m. at their rated load of 60 amperes, thus afford- 
ing a basis for comparison. 

The torque of a motor, which is defined as the tangential force 
that the armature is capable of exerting at a radius of i ft. from 
the center of the shaft, is proportional to the product of armature 
current and field strength. Since the field strength of a shunt 
type constant potential motor is constant, the torque varies 
directly with the armature current and approximately in propor- 
tion to the load. From the above reasoning, it would be expected 
that the torque of a series motor would vary with the square of 
the current since the field current and armature current are the 
same. In the actual design of series motors for railway service, 
however, the magnetic circuit is nearly at the point of saturation 
except at very light loads. The torque-current curve, therefore, 
while slightly concave upward at light loads, is nearly a straight 



MOTOR CHARACTERISTICS. 



37 



line for practically all operating current values since the field 
strength varies but slightly with change of current. In Fig. 1 1 , a 
comparison of the torque-output curves of the three types of 
direct current motors will be found. 

A study of the alternating current motors will reveal the fact 
that all types except the series have approximately the same inher- 















SPEED 


CURVES OF REPRESENTATIVE 
TYPES OF MOTORS. 




























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10 20 30 40 50 60 

Amperes Input to Motor 

Fig. io. 



ent characteristics as the shunt type direct current motor, if the 
starting conditions of some of the former be disregarded. The 
series alternating current motor, as constructed at present for 
railway and hoisting, service, has characteristics very closely 
approximating those of the series direct current motor. 

In order to determine the best class of motor for traction pur- 
poses, therefore, it is only necessary to apply the characteristics 



38 



ELECTRIC RAILWAY ENGINEERING. 



of typical shunt and series direct current motors to the conditions 
of railway service. Such characteristics may be found in Fig. 
12 where A and A' are the speed and torque curves of a series 
motor while curves B and B' represent respectively the corre- 



110 



100 



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2 80 



53 

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TORQUE CURVES OF REPRESENTATIVE 
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B.H.P. Output 

Fig. II. 



sponding characteristics of the shunt motor. The motors from 
which these characteristics were taken were designed for the 
common maximum speed of 22.8 m. p. h. with the particular 
gear ratio used. The torque is expressed in terms of "pounds 



MOTOR CHARACTERISTICS. 



39 



pull at periphery of car wheel" or ''tractive effort" as explained 
under the section on '" Gear Ratio." 

It will be realized at once that a car under most conditions 
found in practice must be able to operate at variable speed. 
Conditions of grades, curves, pedestrian and vehicular traffic, 
necessary stops, etc., demand this. With the geared or direct 



^4 

o 

p. 



24 



20 



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P3 










SERIES AND SHUNT 
MOTOR CHARACTERISTICS 








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20 40 60 80 100 120 140 

Amperes 

Fig. 12. 



connection between motors and car axles usually adopted, 
therefore, a variable speed motor seems desirable. Furthermore, 
a much larger torque is required to start and accelerate a car than 
is necessary to maintain the car at full speed. As the power taken 
by a motor is roughly proportional to the product of torque and 
speed, if large values of torque cannot be obtained at low speeds 



40 



ELECTRIC RAILWAY ENGINEERING. 



the power taken by the motor will be excessive. Reference to 
Fig. 12 will show that with the series motor a large torque is 
available at low speeds, the torque and the current as well falling 
off as the car accelerates and therefore as the demand for torque 



iOOO 




220 



180 



140 



3000 



100 



2000 



CO 



1000 



20 



80 100 120 

Amperes 

Fig. 13. 



180 200 



decreases. Assuming a concrete example, if a tractive effort of 
1200 lb. per motor is required to accelerate a car the series 
motor of Fig. 12 will require but 68 amperes of current while the 
corresponding shunt motor will draw 125 amperes. Assuming 



MOTOR CHARACTERISTICS. 41 

that they are both operating on the same line the power demand 
in the latter case will be nearly double that of the series motor. 

For the above reasons the series direct current motor has come 
into almost universal use for traction service. During the last 
few years, however, the single phase series motor, with practically 
the same characteristics as the direct current series motor, has 
been installed in a number of instances. In several cases in 
Europe and in one instance in this country the polyphase induc- 
tion motor has been adopted where conditions seemed to be 
particularly favorable for constant speed operation. 

Confining the discussion to series motors, the characteristics 
already considered are the torque and speed curves plotted in 
terms of current input. To these should be added the curves of 
efficiency, often plotted both with and without gears, temperature 
rise, and, in the case of alternating current motors, the power 
factor. These characteristics. Fig. 13, may be obtained either 
from design data before the motor is built or by test after its 
completion. 

Assuming that the design of a proposed motor has been tenta- 
tively made, and its dimensions and winding data known, the 
speed, torque, and efficiency characteristics may be found as 
follows : 

E = Impressed voltage, 
e = Counter electromotive force. 
I = Current in amperes. 
T = Torque at i ft. radius in pounds. 
R^ and Rf = Resistance armature and field respectively. 
V = Speed in revolutions per minute. 
Na= Total conductors on surface of armature. 
Nf = Turns on one field pole. 
^= Flux per pole in Maxwells. 
p = Number of poles. 

b = Number of paths in parallel on armature. 
A = Area cross section magnetic circuit at air gap. 
1 = Length magnetic circuit. 
/^ = Equivalent permeability magnetic circuit. 
W= Power delivered to the shaft of motor expressed in 
watts. 



42 ELECTRIC RAILWAY ENGINEERING. 

From the experimental definition of the volt: 

60 X 10^ b 



(I) 



60 X 10^ be 

or V = — -— T (2) 

Na<^p ' 

but if leakage and armature reaction be neglected, 

4 TrNflA/x 



Simplified 

but 

therefore 



47 . 7 X 10^ bel 
V=^^— ^ (4) 

e = E-I(R,+ R,) (5) 

47.7xio^bl[E-I(R,+ R,)] 

N^pNflA/. ^ ^ 

As all factors in the right hand side of equation (6) are either 
constants of the design or dependent upon current, a series of 
assumed values of current will give corresponding values of speed 
(V) from which the speed characteristic may be plotted. It will 
be seen from equation (2) that if (^) be constant because of field 
saturation, the speed (V) will vary directly with the counter 
e. m. f. (e). Since, however, the voltage drop due to resistance is 
a small percentage of the impressed voltage, it may be said that 
the speed of a series motor varies with the voltage impressed upon 
it if load conditions remain the same. This fact is of importance 
in the design of car control systems. 

With reference to the torque characteristic and neglecting iron 
losses, 

W = el (7) 

2 ttVT X 746 

W= -^ (8) 

33000 



whence 



r^_ 33000 eIN ^ # 
2 TT X 746 X 60 X 10^ be 



MOTOR CHARACTERISTICS. 



43 



or 



0.117 IN^# 
io«b 



(10) 



If the flux ((f)) be assumed constant, which would be the case with 
the magnetic circuit saturated, equation (10) proves that the 
torque of a series motor will vary directly with the current as 
previously stated. 

While the efficiency and temperature characteristics can be 
very closely approximated in advance by means of empirical 
formulae, it is usually customary to determine these values roughly 
by comparison with other machines of similar design which have 
been previously constructed and to await the test for accurate 
results. 



AAA/VW\A 



^TJMOTnr^ 








Fig. 14. 



Several methods of testing are available for the determination 
of all the characteristics of the motor when constructed. Three 
methods will be briefly outlined, of which the one involving the 
apparatus most available may be selected. 

Prony Brake Method. — This method is probably the simplest 
of the three and may be used where plenty of power is available 
for the operation of the motor up to 50 or 100 per cent, overloads. 
As the name implies, the motor is loaded by means of a prony 
brake from which the torque may be directly determined, while 
the current and speed are read directly by means of an ammeter 
connected in series with the motor at (A), Fig. 14, and a tachom- 
eter. The resistance (R) may be inserted, if necessary, to 
maintain constant voltage across the motor. The efficiency curve 
may be obtained by making a series of calculations from the 



44 



ELECTRIC RAILWAY ENGINEERING. 



following formula (13) with varying currents. It is believed that 
the derivation of the formula is self explanatory. 
If T' represent torque at pulley at i ft. radius. 

2 ttVT' 

Output (h. p.) = 



Input (h. p.) 



33000 
EI 



Efficiency = 



746 

0.142 VT' 
EI 



(II) 
(12) 

(13) 



Pumping Back Method. — For this test two motors, identical 
in design and construction, are necessary, but the method has the 
advantage of a relatively small power demand as the losses alone 
are supplied from outside sources. 




Fig. 



Two motors are placed in alignment with shafts end to end and 
mechanically clutched together. They are so connected, Fig. 15, 
that one machine, acting as a motor with a separately excited 
field, drives the other as a generator. The latter has a series 
connected field. By varying the field strength (F') by means of 
the resistance (R) the current (A') may be controlled from no load 
to overload. The output of motor No. 2, if the losses are supplied 
from the external source (S) is the product of the readings (V) 
and (A'). This value of power, reduced to foot pounds per 
minute and divided by 27: times the speed of the set, determines 



MOTOR CHARACTERISTICS. 45 

the torque. Speed and torque plotted against current in 
amperes read from meter (A') furnish the two principal motor 
characteristics. 

In order to find the efficiency, for which a knowledge of the 
losses is necessary, the assumption is made that the combined 
iron and friction losses of the two machines are equal. Since the 
I^R loss of No. 2 has been eliminated from the calculation by the 
fact of its separate excitation, the losses represented by the power 
(AV) must be made up of the following: 

Friction losses of both machines. 

Iron losses of both machines. 

I^R losses of both armatures. 

I^R losses of No. i field. 
If the resistances of both armatures and fields are known, the 
I^R losses can be readily calculated for the various values of 
current. These losses subtracted from (AV) leave the total 
iron and friction losses of the two machines, one half of which, 
according to the above assumption, is chargeable to each motor. 
Thus the losses and therefore the efficiency of the motor under 
test become known and the efficiency characteristic may be 
plotted. If a more detailed analysis of iron and friction losses is 
desired, additional tests with different connections must be made.^ 

The two temperature curves of Fig. 13 showing respectively 
the time required for the motor to rise 75° C. above the room 
temperature when starting cold and the time to rise 20° C. above 
the temperature of 75° C. for the various currents in the motor 
circuit, are of the greatest value in selecting the proper motor 
for a given service not only, but for determining the tempera- 
ture rise corresponding to various overloads which the motor will 
usually be called upon to carry for short intervals of time. The 
values from which these curves may be plotted can best be ob- 
tained by actual test preferably with the connections of Fig. 15, 
separate runs being made, of course, for each value of current. 
Thermometers placed on the various parts of the machine during 
the run indicate when the desired temperature has been reached 
and the time for such rise may then be plotted against the con- 
stant value of current maintained during the test. Additional 

^ See "Experimental Electrical Engineering" by V. Karapetoff, pp. 406-407. 



46 ELECTRIC RAILWAY ENGINEERING. 

thermometers may be applied to determine the temperature of 
rotating parts at the end of the test and the hot resistance of the 
windings taken to determine by calculation the internal tempera- 
tures of the coils. 

Motor Used as a Generator. — In this case the motors are 
mechanically clutched together as in the "pumping back" test, 
one being used as a motor to drive the other as a generator. The 
latter is loaded by means of a water rheostat as shown in Fig. i6. 
The calculations for losses and efficiency are very similar to those 




Fig. i6. 

in the previous test, this method differing from the former prin- 
cipally in the type of load used. These connections are often 
used by the manufacturing companies for the one-hour heat run 
usually applied to railway motors. 

Gear Ratio. — Since a suitable design for a railway motor de- 
mands a speed much higher than that at which the car axle should 
be driven in ordinary installations, single reduction gearing is 
introduced between the motor shaft and the car axle, a pinion 
upon the former engaging a gear keyed to the latter. 

It has become customary in railway practice to express this 
gear ratio as an integer, or 

No. teeth in gear 

Gear Ratio = "z , — : 7—. — (14) 

No. teeth m pmion 

As it is most convenient to plot the characteristic curves of 
railway motors in terms of forces at the periphery of the car wheel 
and speeds in miles per hour travelled by the car, it is obvious 
that a given group of such curves is dependent upon a single 
definite car wheel diameter and gear ratio. With a change of 
gear ratio, however, the motor speed remaining the same, the 
speed of the car will change in the inverse proportion while the 



MOTOR CHARACTERISTICS. 47 

tractive effort will, of course, vary in direct proportion to the 
change in gear ratio. 

The torque and speed characteristics may, therefore, be changed 
to apply to a new gear ratio by the use of the proportions given 
in equations (15) and (16). 

New Speed Old gear ratio 



Old speed New gear ratio 
New tractive effort New gear ratio 



(IS) 

(16) 



Old tractive effort Old gear ratio 

Motor characteristics thus changed are represented by the 
dotted lines'of Fig. 13. 



CHAPTER VI. 

Speed Time Curves (Components.) 

Weight of Car. — ^From the familiar relation Force = Mass x 
Acceleration expressed in the formula: 

F = ma (17) 

it is clear that the weight of the car, complete with its equipment 
and load, will enter into the calculations for the speed time curve 
as an important factor. The above equation may, however, be 
reduced to a form more convenient for railway application as 
follows : 

m = w/g (18) 

where (w) represents the weight in pounds and (g) the accelera- 
tion of gravity (32.2). Equation (17) becomes with this substi- 
tution 

wa 

F = (19) 

32.2 

Changing to the more convenient units of miles per hour in place 

5200 
of feet per second by means of the constant i m. p. h. = -- — = 

3000 

1.467 ft. per sec. or (a) = 1.467 A, when (A) is expressed in miles 
per hour per second and substituting 2000 W in place of (w) 
expressed in pounds equation (19) becomes 

WA X 2000 X 1 . 467 

F = ^ ^^^ = 91.1 WA (20) 

32.2 

In order, therefore, to accelerate a car at a rate of i m. p. h. 
p. s., a net force of 91. i lb. must be exerted for every ton weight 
of car. It must be remembered that this net force available 
for acceleration is only that which remains after all frictional 
resistances of the car have been overcome. 

It is now possible to obtain a relation between the tractive effort 
of the motors comprising the car equipment and the acceleration 

48 



SPEED TIME CURVES. 49 

that this tractive effort will produce for a given weight of car. 
This will obviously depend upon whether a two or four motor 
equipment is used. Equation (20) may be written 

91. 1 W 
if n = Number of motors on car 
Pj^ =Net tractive effort per motor. 

From the above equation it will be seen that the acceleration is 
inversely proportional to weight of car. 

Bearing and Rolling Friction. — In studying the various 
retarding forces which have to be overcome by the motors in car 
operation and which must, therefore, be subtracted from the 
gross tractive effort of the motors in order to determine the net 
effort available for acceleration, it seems logical to consider first 
those forces acting under the normal conditions of a straight level 
track. Among these forces are found the friction of armature 
and axle bearings. The axle friction, which is usually the greater 
of the two, varies with the pressure on the bearing, and therefore 
with the weight of the car for a given truck arrangement. Both 
frictional resistances vary very nearly in proportion with the 
speed. In building up an empirical formula for train resistance, 
therefore, expressed in pounds train resistance per ton weight of 
car, it would be expected that bearing friction would be represented 
therein by a constant term added to a term varying with speed. 

There are found to be present, however, in the operation of a 
car other frictional forces exerted between the wheels and rails. 
These forces have been termed "rolling friction." They are 
caused partly by the rubbing of the wheel flange against the head 
of the rail and partly by the fact that there is apparently a slight 
depression in the rail under each wheel out of which the wheel 
must be forced against an appreciable resistance. This effect is 
more marked with a greater distance between ties or in cases 
where rail spikes have become loosened, allowing considerable 
vertical motion to the rail as the car passes over it. Since the 
flange friction previously mentioned is considerably increased if 
the track gauge is not maintained constant, the entire item of roll- 
ing friction may vary greatly with the condition of the track. As 
4 



50 ELECTRIC RAILWAY ENGINEERING. 

this resistance will also vary with the speed and weight of the car 
for a given track, both bearing and rolling friction may be repre- 
sented by a single constant plus a second term varying with speed. 

Air Resistance. — The amount of resistance offered to the 
motion of the car by the air is very surprising, especially in the 
case of single cars at relatively high speeds. Not only is there 
considerable resistance offered to the front cross section of the 
car as it cuts through the various strata of air but the friction of the 
air upon the sides of the cai and the eddies and suction produced 
at the rear cause a considerable retarding effect upon the motion 
of a train. This suction phenomenon may readily be observed 
at the rear of a high speed train by noting the motion which it 
conveys to cinders and light objects found along the track. 

This air friction upon the various portions of the car has been 
more or less successfully measured in train resistance tests, 
but there still exists a wide difference of opinion regarding its 
absolute value. It is generally conceded, however, that the 
front and rear end resistances are proportional to the cross-sec- 
tional area of the car from car axle to roof and that the side resist- 
ance of a single car is approximately one-tenth of the sum of head 
and rear resistances. Since the side resistance is much smaller 
than the end resistance it would be expected that the total air 
resistance per ton weight of car would be very much greater for a 
single car than for a train. This has been found to be so marked 
in the tests carried out that it is usually impractical to operate a 
single car much over 60 m. p. h., while a train of many cars 
may be operated at much higher speeds without serious loss. 
While this air resistance is a comparatively small quantity at low 
speeds, it is generally considered to vary with the square of the 
speed and is therefore a very formidable factor at high speeds. 

As a result of the various train resistance tests which have been 
made by determining the deceleration of cars and trains while 
coasting from different initial speeds to a standstill on a straight 
level track, a number of empirical formulae have been suggested 
and used with varying degrees of accuracy in train calculations. 
The tests which have been made comparatively recently with 
electric equipment, with which the power is much more accurately 
measured than in steam locomotive tests, may be represented by 



SPEED TIME CURVES. 



51 



the curves of Fig. 17, plotted in pounds per ton train resistance 
for 25 ton cars against speed in miles per hour. This train 
resistance includes bearing and rolling friction and air resistance 
upon the entire car or train. 



90 










TRAIN RESISTANCE CURVES, 








85 
80 








25 ION CAR WITH VARYING SPEED 




















,^/ 


/ 


/ 






^ 


^ 


75 












C7 


.^y 


/^ 




^y 


y' 






4O 












/ 


y 


i/ 




y 








G5 
60 

^5.5 










/ 


f 


/ 


V 


y 






















/ 




/ 


/ 


/^ 








\ 


c$^ 












f 




/ 


/ 








^^ 


^ 






% 50 








/ 


/ 




/ 








/ 


y 










a 40 






i 


/ 


/ 


/ 






y 


/ 


















/ 


/ 


' 




/ 


/ 














35 
30 

25 
30 




i 


1 , 


> 


/ 




/ 


/ 


















/ 


/ 


/ 




A 


/ 




















/ 


// 


/ 


/ 






















// 


7 




/ 






















15 
10 


;/ 


/ 


/ 




























\ 


/ 






















5 


1 


// 




\ 

























5 10 15 20 25 30 35 40 

Train Resistance in Lbs. per Ton 

Fig. 17. 

The empirical formula from which these curves were plotted 
and which probably approximates most closely the true train 
resistance in practice is represented below. 

n — I. 

(22) 



^R 



=50 .002 2 



10 



R = Total train resistance in pounds per ton weight of train. 
W = Weight of train in tons. 
V = Speed of train in miles per hour, 
a = Area of cross section of front end of car or locomotive 

above axle expressed in square feet. 
n== Number of cars in train. 

^ See "Electric Traction" by A. H. Armstrong. 



52 



ELECTRIC RAILWAY ENGINEERING. 



In this formula the first two terms express the rolling and bear- 
ing friction while the last term determines the resistance due to air 
friction and suction. 

The effect of increased weight of cars upon train resistance at 
constant speed is very clearly shown in the curves of Fig. i8, 
which are plotted from the same formula. It must be remem- 
bered that this effect is entirely separate from the extra tractive 



d 
o 

fl 

-p 

,^ 

be 

I 

60 
55 
50 
45 
40 
35 
30 
26 
20 
15 
10 
5 








































TRAIN RESISTANCE CURVES. 

SINGLE CAR OF VARYING WEIGHT 

AT CONSTANT SPEED. 














































































































































1 


\ 










\ 


















'l ' 










\ 






















\ 




























\ 


\ 












\ 
















\ 


\ 


V 












\ 














\ 




\ 














\ 


«4 


^jt. 










\ 


\ 


\, 














s 


ft 


^ 








\ 




\ 


s. 


























\ 




\ 


N, 


8-r , 
























\ 






<^ 


^ 






















^ 


^ 


^.p. 


u. 











































10 15 20 25 30 35 

Resistance in Lbs. per Ton 

Fig. i8. 



40 



effort necessary to accelerate the heavier cars and therefore 
represents an additional negative force or resistance which the 
motors are called upon to overcome when operating heavy rolling 
stock. 

Rotative Inertia of Wheels and Armature.— It will be 
remembered from mechanics that if two different rotating masses 
of different inertia are acted upon by similar propelling and simi- 
lar resisting forces respectively, the mass having the greater in- 



SPEED TIME CURVES. 53 

ertia will have the lower value of acceleration or decleration as 
the case may be. 

From this fact it would be expected that the relatively large 
inertia of the rotating elements of the car, including motor arma- 
tures, gears, pinions, axles, and wheels would tend to reduce the 
acceleration when the car is starting and the deceleration when 
coasting and braking. This inertia factor must be taken into 
consideration in the accurate calculation of speed time curves as 
follows : 

The energy of rotation — 



^I M^^k^ 



E = — = (23) 

2 2 

since I = Mk^ (24) 

where w = Angular velocity, 
I = Moment of inertia, 
M = Mass, 

k = Radius of g)Tation. 
These fundamental formulae will be applied to this particular 
problem with the following nomenclature : 
n^ = Number of pairs of wheels on car. 
na = Number of armatures on car. 
W^ = Weight of each pair of wheels and axle in tons. 
W^ = Weight of each armature in tons. 
k^ = Radius of gyration of wheels and axle. 
k^ = Radius of gyration of armature, 
r = Radius of wheels in feet. 
A = Acceleration of car in m. p. h. /sec. 
V= Velocity of car in m. p. h. 
v= Velocity at extremity of radius of gyration, 
g = Acceleration of gravity. 
G = Gear ratio. 
W= Weight of car in tons, 
p = Net tractive effort at periphery of wheel. 
Considering first the wheels and axles : 
From equation (23) 

n W (k wY 
E^= (25) 



54 ELECTRIC RAILWAY ENGINEERING. 

But 

k^o) = V (26) 

Substituting 

W v' 

Ew = n^^ (27) 

Since the velocity of the periphery of the car wheel is the same 
as that of the car, if it be assumed that no slipping occurs, 

W /k \' 
E.-„^(-v) (.8) 

or, in other words, replace n^W^ with the equivalent weight 

KV 

7 j n^W^ if (V) is used in (27). 

In a similar manner, remembering that in transferring armature 
values to those at the periphery of the wheel the gear ratio (G) 
must be introduced, 

E.=„.^(~^GV) (.9) 

from which the equivalent weight is( — G ) n^W^ 

By adding the new values of equivalent weight, expressed in 
tons, necessary to overcome rotational inertia, therefore, formula 
(20) may be corrected to read 



F = 9i.i A 
Since the radius of gyration 



k^\ 2 /k G\ 2 



w w ; 



(30) 



and all revolv'ng parts to be considered in electric traction are 
cyl'nders revolving about their axes, 

I = M^ (32) 

2 

k=4= (33) 

\/ 2 



SPEED TIME CURVES. 55 

In order to determine approximately the magnitude of the 
inertia of rotating parts the following concrete values, which are 
often found in practice may be assumed. 

nw = n^ . =4 

W^=-i5oolb. =0.75 ton. 

Wa=7oolb. =0.35 ton. 

r= =1.375 ft. 

2 X 12 

^W=,^ ,, y- =0.97 ft. 

2 X I2V 2 

14 in. 

k_= ;-- =0.412 ft. 

2 X I2\/2 

A=i m. p. h. /sec. 
0=19/52 =2.74 

W = 25 tons. 
Substituting in (30) 

F = 9i.i (25+1 .49+ .944) = 2500 lb. 

or 100 lb. per ton. In other words, the net tractive effort 
necessary for translation must be increased approximately 9 . 8 
per cent, for this car in order to overcome the inertia of rotating 
parts for an acceleration of i m. p. h. /sec. 

For approximate calculations, 100 lb. per ton is often as- 
sumed for the net tractive effort without calculation of rotative 
inertia. The following table taken from the Standard Handbook 
will give other values which may be assumed under varying 
conditions. 

TABLE V. 
Per Cent, of Total Tractive Effort Consumed in Rotating Parts. 

Electric locomotive and heavy freight train 5 per cent. 

Electric locomotive and high speed passenger train 7 per cent. 

Electric high speed motor cars 7 per cent. 

Electric low speed motor cars 10 per cent. 

Grades. — Whenever a grade is encountered it is not only 
necessary to provide an additional tractive effort to overcome 



S6 



ELECTRIC RAILWAY ENGINEERING. 



linear and rotational inertia, but it is also necessary to make use 
of some of the tractive effort of the motors in actually lifting the 
car through the vertical distance represented by the grade. In 
other words, referring to Fig. 19, the weight of the car (W) may 
be resolved into the two forces (N) and (W sin a) which are 




Fig. 19. 

normal and parallel to the track respectively. The reaction of 
the track balances the former while a force proportional to the 
latter must be supplied by the motors of the car. As the angles 
(a) and (a') are equal it is obvious that this force is proportional 
to the grade and amounts to o.oi x 2000 = 20 lb. per ton weight 
of car for each per cent, of grade. If the car is on a down grade 




this force is available for producing acceleration and is therefore 
added to the tractive effort of the motors. 

Curves. — Before it is possible to consider the resistance offered 
to the passage of a car or train by curves in the track, it is neces- 
sary to understand clearly the method of rating curves. In city 
streets where sharp curves are met with, they are usually desig- 



SPEED TIME CURVES. 57 

nated by their radii, e.g., a curve of 30 ft. radius. On private 
rights of way, however, in suburban and interurban construction 
it has been customary to designate curves in degrees of central 
angle subtended by a chord of 100 ft. Referring to Fig. 20, if 
angle (^) is drawn so that it is subtended by the chord (ac) of 
100 ft. and ((f)) = 1°, then the radius (Ob) necessary to make 
this assumption correct is found as follows : 

50 
tan 30'= .0087 = — —or (Ob) = 5730 ft. 

The radius of a 1° curve is therefore 5730 ft. 
If now (ab) be moved toward (O) such a distance as to make 
(Oe) = (eb) 

6 50 
tan — =--^= .oi7t; = tan 1° or ^ =2° 
2 2865 ^^ 

Therefore, curvature in degrees 



radius 



As a car enters a curve there is, of course, a tendency to ride 
over the outer rail and there occurs between the flange of the car 
wheel and the head of the rail considerable frictional force 
tending to cause the car to follow the rail but at the same 
time retarding the motion of the car. This force must be 
considered as an additional resistance which manifests itself in 
frictional heat. 

The amount of this resistance has been approximated from 
test data and it is conceded that it is directly proportional to the 
curvature in degrees. Values ranging from 0.52 lb. to i lb. per 
ton weight of car per degree curvature have been obtained but 
good practice at present stipulates 0.6 lb. per ton weight of car 
per degree curvature. When the car is on a curve, therefore, an 
additional force of o . 6 W x degrees curvature must be subtracted 
from the gross tractive effort in addition to all resistances pre- 
viously considered. 

Probably the best method of summarizing the discussion of 
train resistance is to express in terms of a formula the derivation 



58 ELECTRIC RAILWAY ENGINEERING. 

of the net tractive effort available for acceleration from the 
gross tractive effort obtained from the motors, thus — 

p=P-f±g-c - (35) 

where 

P = Gross tractive effort of motors in pounds per ton. 

p = Net tractive effort available for acceleration in pounds 

per ton. 
f = Train resistance due to bearing and rolling friction and 

air resistance in pounds per ton. 
g = Resistance due to grades in pounds per ton. 
c = Resistance due to curves in pounds per ton. 

The use of this net tractive effort (p) in calculating the acceler- 
ration of a car or train will be discussed in detail in the following 
chapter. 



CHAPTER VII. 
Speed Time Curves (Theory). 

Ha\ing considered in detail the various factors entering into 
the speed time curve, the methods of plotting same may now be 
considered. Two methods are in general use, the so-called "cut 
and try" method which involves considerably more time for its 
performance but which is the more accurate, and the "straight 
line" method which assumes all portions of the diagram made 
up of straight lines, thereby simplifying the calculation at the 
expense of the introduction of slight errors. The former and 
more accurate method will first be considered, for only through 
the complete analysis of the correct curves can a thorough 
understanding of electric car performance be obtained. 

The distance between the two consecutive stops having been 
determined, it is next necessary to select the proper schedule speed 
for the run, i.e., the average speed, which if maintained constant 
throughout the run would bring the car to its destination in the 
required time. This speed is usually determined from traffic 
studies, and is, of course, dependent upon the train schedule of 
the entire system. With the distance and schedule speed deter- 
mined, the time required for the run can be calculated and the 
limits of the curve laid off graphically to scale as (OT) in 
Fig. 21. 

The nomenclature which will be used is as follows: 

T.E. = Gross tractive effort per motor in pounds. 

P = Gross tractive effort at periphery of car wheel in 

pounds per ton. 
p = Net tractive effort in pounds per ton. 
V = Speed corresponding to (TE) in m. p. h. 
I == Current corresponding to (TE) in amperes. 
A = Acceleration in m. p. h./sec. 
D = Deceleration in m. p. h./sec 

59 



6o 



ELECTRIC RAILWAY ENGINEERING. 



V = Schedule speed in m. p. h. 

S = Length of run in feet. 
s s', etc. = Distances in feet. 

T = Time for entire run in seconds. 
1,1'; etc., =Time for portions of run in seconds. 

f = Train resistance in pounds per ton. 

g = Grade resistance in pounds per ton. 













































40 






SPEED AND DISTANCE CURVES. 










^ 


^ 


































y 


^ 


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,1 


/ 


'A 


f 














35 


















^ 


^ 




^ 


















30 












^ 








A 


/ 








r' 




















y' 








/ 


4- 


-^ 






\ 




















-^? 


1 


^ 

\ 








^ 


Xr 










\ 
\ 
\ 












lo 








1 




^ 


k; 


^ 


/- 




\ 








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20 




jlj 




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1 


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s" 


y 


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I 
\ 
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1 
1 




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/ / 




V 


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t^ 


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\ 




1 

1 
i 




// 










X 


N 


V 




\ 
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15 




/ 1 




1 

1 


// 


/ 


x 
\ 


^ 








V 


^^ 


<^ 


\ 


\ 










10 




' 1 
1 
1 




1 


y 






^ 


^^>. 








\ 
\ 


\ 


S 


K 










/ 


1 




/ 












^v 


^ 

\ 






\ 

\ 


N 


^371 




'A; 








/ 


1 
1 


J 


'A 
11 






















\\ 


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5 


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/| 




















X 




\ 


M' 


n" 








n 


L 


^ 


0\ 


i' 












q" 










v^ 


^0^4 


T 









4000 



3500 



3000 



2500 



2000 



1500 



1000 



500 



10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 

Fig. 2 1. 

c = Curve resistance in pounds per ton. 
b = Braking resistance in pounds per ton. 
W = Weight of car in tons, 
n = Number of motors on car. 
Wi = Weight of car per motor in tons. 
Referring to Fig. 21. 

S 

OT = T = ;- -7- (36) 

Vx 1.467 ^^ ^ 

The acceleration (A) must be assumed sufficiently large to 



SPEED TIME CURVES. 6 1 

enable the desired schedule to be made and yet not so great as 
to be of inconvenience to passengers. The method of calculating 
the net tractive effort (p) has been previously explained in formulas 
and it will therefore be considered as a known quantity. 
The gross tractive effort per ton may now be found 

P = (p + f±g + c) • (37) 

The sign of the grade resistance (g) depends, of course, upon 
whether the car is ascending or descending the grade; in the 
latter case the sign is negative and the gross tractive effort 
necessary is decreased by the presence of the grade. 

The weight of car which must be accelerated by each motor is : 

W 

The gross tractive effort which the motor must exert is therefore : 

W 

T.E.=PWi = -^(p+f±g+c) (39) 

Referring to the characteristic curves of the motor which has 
been assumed as probably of the correct design for this service 
the gross tractive effort (T.E.) is found to correspond to a current 
I (Oa, Fig. 22) and at this current the speed is v (ab. Fig. 22). 
The motors of the car will be able to maintain this rate of acceler- 
ation (A) as long as they can be supplied with current I = Oa. 
As the speed increases, however, the current and therefore the 
tractive effort will decrease unless the voltage applied to the motors 
is increased. This is the function of the control equipment 
whether it be of the rheostatic, series parallel, or auto-transformer 
type. Until such time as the voltage impressed upon the motors 
reaches the maximum value possible with the particular control 
equipment in use the assumed value of acceleration (A) may be 
used for calculation. In other words the acceleration portion of 
the speed-time curve may be drawn as a straight line from O with 

/dv \ . 
a slope of ( — = A I until a speed is reached corresponding to 

(v = ab), Fig. 22. This line is drawn as Ob' in Fig. 21 where 
a'b' = ab, Fig. 22. 

Beyond the point (V) the ''cut and try" method using incre- 



62 



ELECTRIC RAILWAY ENGINEERING. 



merits of speed and time must be used. The time, t = Oa' corre- 
sponding to point b', can readily be calculated from the equation 

V a'b' 

(40) 



t = 



A A 



Assuming a small increment of speed beyond point (b') = dv, 
the new speed is (v + dv)=ec. Referring to the characteristic 



30 



25 



20 



M5 



10 



SPEED AND TORQUE CHARACTERISTICS 
OF WESTINGHOUSEfr56 MOTOR 





\ 




















\ 




















\ 


I 




















V 




















N 


V 




















\ 


1^^^c 




















1 




£^- 
















1 

1 
1 






""^^ 


2tS" 












1 

1 
1 




















1 

1 






-.1- ^'W' 


e>^ 


f> 










1 
1 
1 




^,^o^> 




^ 












1 
1 


^ 

^ 


^ 














^ 


1 


r 














^ 






1 


£ 













4000 
3500 
3000 
2500 
2000 
1500 
1000 
500 



20 40 60 80 100 120 140 160 180 200 
Amperes 

Fig. 22. 



curves (Fig. 22), this speed (ec) corresponds to a gross tractive 
effort T.E.'' = (ef). It is now necessary to determine what accel- 
eration this tractive effort can produce as follows : 

T.E.' 



Net tractive effort p' = ~^ - f ± g' - c' 



(41) 



SPEED TIME CURVES. 63 

If the speed increments are selected sufficiently small the 
value of (f) will not be materially different from (f), although for 
accurate work substitution should be made of the resistance from 
the train resistance curves, Fig. 17, for the average speed repre- 
sented by the increment (dv). The distance curve explained 
below will determine the portions of track corresponding to 
various points on the speed time curve, thus permitting correct 
values of (g) and (c) to be selected. In many cases these latter 
values do not change materially throughout the calculation. 

Having determined the new value of net tractive effort (p') 

p' 
A' = — A (42) 

P 

where (A') is the new acceleration for the increment of speed (dv) . 

The time required to traverse the distance (ds) may be calculated 

from the equation 

dv 
dt=^, (43) 

The coordinates of the next point upon the acceleration curve 
are therefore known to be (v + dv) =g'b'' and (t + dt) =0g' and 
the point may therefore be plotted as (b'') . 

If this procedure be continued, assuming new increments of 
speed and calculating the corresponding values of the time 
increments, the complete acceleration curve may be plotted. 
This curve will become horizontal when the acceleration reaches 
zero; or, in other words, when the gross tractive effort of the 
motors is completely balanced by the resistances so that no net 
tractive effort remains to produce acceleration. With no change 
in grade or curvature of track the car will continue running at 
constant maximum speed until the power is shut off. 

Coasting. — The amount of coasting permissible in a given 
run varies widely. In some instances where schedules are very 
conservatively planned and the equipment more than adequate 
for the demands made upon it, excessive coasting is introduced, 
while in heavy suburban and elevated service, braking is often 
begun as soon as power is shut off, the coasting portion of the 
curve being entirely eliminated. In order to be able to make up 
time in case of delay, however, some coasting should be provided 



64 ELECTRIC RAILWAY ENGINEERING. 

for in the speed time curve, the time involved in this portion of 
the run acting as a storage reservoir for a hydraulic plant 
since it may be drawn upon if necessary to maintain normal 
schedules. 

In order to plot an absolutely accurate coasting curve the 
"cut and try" method should be used, since the average speed 
during the coasting period, from which the train resistance factor 
(f) is obtained, is difficult to predetermine and for the further 
reason that the resistance (f) does not vary directly with the 
decrease in speed. It is customary, however, to consider the 
coasting portion of the diagram as a straight line, i.e., to assume 
the deceleration constant, and to select the value of (f) from appro- 
priate resistance curves (Fig. 17) for an approximate average 
speed during coasting, or even to assume (f) directly. This value 
is often taken arbitrarily at 15 lb. per ton. 

With the value of (f) known, the deceleration is 

-(f±g + c) 
Dc = — -^^A (44) 

P 

from which the increment of time (dt) corresponding to an 
assumed change of speed (dv) may be calculated as follows : 

dv 
dt=— (45) 

c 

The coasting line may then be drawn through (f), Fig. 21, 

dv 
with a slope D^ = -— . Such a line is (f k). Fig. 21 (f ), being 

any point arbitrarily selected upon the acceleration curve. The 
line (f'k) determines the direction but not necessarily the exact 
position of the coasting line. 

Braking. — Since the speed time curve must cut the time axis 
at T, Fig. 21, in order that the run may be completed in the pre- 
determined schedule time, the braking line can best be drawn back 
from T, the slope being determined by the assumed braking 
deceleration as in the case of the coasting curve. As in the case 
of acceleration this rate must be selected sufficiently high to enable 
the schedule to be maintained and yet not prove disagreeable to 
passengers. In heavy suburban and elevated traffic where speed 



SPEED TIME CURVES. 65 

is relatively high and headway short the braking rate must 
necessarily be high. An average figure often assumed is i . 5 
m. p. h. /sec. The braking line in Fig. 21 is represented by Tr'. 

The area under the speed time curve obviously represents the 
distance travelled during the run. In plotting the curve, there- 
fore, especially if the distance time curve is not simultaneously 
plotted, it is advisable to determine the area of the diagram occa- 
sionally by means of a planimeter as a check upon the distance. 
In closing the diagram, also, after the braking line has been 
drawn, the coasting line (I'm') must be so located parallel to (f'k) 
that the area of the diagram will correspond to the distance 
travelled between the stops under consideration. The completion 
of the diagram is therefore a "cut and try" method. 

In order that this method of plotting speed time curves may be 
more clearly understood a concrete example of a typical problem 
will be found in Chapter IX. 



CHAPTER VIII. 

Distance, Current, and Power Time Curves 

(Theory) . 

The speed time curve having been determined, the secondary 
curves which are dependent thereon may now be given consider- 
ation. 

Distance Time Curves. — The distance time curve which is 
usually plotted simultaneously with the speed time curve is also 
obtained by the "step by step" method, the series of increments 
of time determined for the speed time curve together with the 
corresponding average speeds during the increment being used to 
calculate the increments of distance as follows : 

ds = *^x 1.467 dt (46) 

2 

These increments of distance when plotted form the curve 
(On'p'), Fig. 21, having ordinates expressing distance in feet cor- 
responding to abscissas of time in seconds. Such a curve rises 
slowly as the speed increases, maintains a constant slope, and 
gradually approaches the horizontal during the coasting and 
braking periods. 

■ Current Time Curve. — In order that the power which will be 
taken by a car on a given run may be predetermined the current 
and voltage time curves must be plotted. Since the voltage is 
usually assum_ed constant at some average value which may 
reasonably be expected to obtain over the entire line its graphical 
representation is merely a straight horizontal line. 

With the current, however, it will be remembered that the 
control equipment is expected to maintain practically constant 
current values in each motor until the net tractive effort falls 
below that necessary for the initial assumed acceleration. This 
point, which is represented by (b'), Fig. 21, has its time coordi- 
nate definitely fixed. The current per motor (I), as found from 

66 



DISTANCE, CURRENT, AND POWER TIME CURVES. 



67 



the characteristics for this particular speed might be plotted as 
constant from the start to a point (t = oa'). Since, however, the 
series parallel control is ordinarily used and the current con- 
sumption for two motors is the important consideration, it is 
usually assumed that during the first half of the time (oa'). Fig. 
21, the motors are in series and during the latter half period in 
parallel. The current consumption for two motors is, therefore, 
double the value in the latter or parallel half that it is in the 
first or series half of the constant acceleration portion of the run. 







































































































CURRENT TIMECURVES 














s 




















































































< 

360 












































k 




b" 


















-^, 
















320 
280 
240 
200 














\ 








,^ 










s 


\ 




















\ 


\ 




/ 


r 












s 


\, 




















\ 


/ 


/ 
















s 


k. 










0" 


1 









\^ 


1 




















V 


■ — 


n 




160 

120 

80 

40 




















\ 


s 


































0' 


( 






S 


















































































a" 








9 


1 






















?" 





5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

Time in Seconds 

Fig. 23. 

Thus two of the motors of a four motor equipment would have a 
current-time curve during the constant acceleration period rep- 
resented by (OO'afg), Fig. 23, while the current of all four motors 
or better, the current per car for the same period may be deter- 
mined at any instant from the curve (OCfkb'') of the same 
figure. Since the two sets, of two motors each, are in parallel 
with each other the total current per car in the series connection 
(OO'O is double (00') and the corresponding ''parallel" current 
(a'V) is double (OO'O- 
Beyond the point b'^ because of the increase of speed, the 



68 



ELECTRIC RAILWAY ENGINEERING. 



current begins to decrease, each point on the curve being readily 
determined by referring back to the motor characteristic curve, 
Fig. 22, for the current values corresponding to the various 
coordinates of speed and time on the speed time curve. The 
complete current curve up to the time (oqO, Fig. 21, where the 
current is shut off, may then be plotted as (OCfkb'^lq'), 
Fig. 23. 

Power Time Curve. — The power taken at various times 
during the run can be very readily represented graphically with 







































































































POWER TIME CURVES 
AVERAGE VOLTAGE 500 














































180 




















































































h 




j<: 












^ 






s. 


















'^1 




\ 


140 








\ 








y 


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\ 


\ 




















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V 




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/ 












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100 










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o{' 










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1, 




















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60 




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20 












































0, 














9 


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10 20 30 40 50 60 TO 80 90 100 

Time in Seconds 

Fig. 24. 

the same abscissae as the above current curve but with ordinates 
which are the products of the current curve ordinates and the 
average assumed voltage. Since the voltage is constant, the 
power diagram (OiO/'fik^b/'liq/) , Fig. 24, will take the same 
form as the current curve. 

If alternating current series motors are being considered, with 
which the series parallel control is seldom used, the current per 
motor and also per car will remain fairly constant throughout the 
constant acceleration period, i.e., during the time (Oa''), Fig. 23. 
Since the voltage impressed upon the motors during this period is 



DISTANCE, CURRENT, AND POWER TIME CURVES. 



69 



usually varied by means of an auto-transformer or induction 
regulator, neither of which involve the power losses incurred by 
the direct current rheostatic and series parallel control systems, 
the voltage curve is assumed as a straight line between the starting 
voltage and maximum operating secondary voltage. This start- 
ing voltage, or the voltage necessary to produce the initial tractive 
effort may be determined from motor tests while the maximum 
operating secondary voltage is usually that at which the motors are 
designed to operate. 

If the product of the ordinate s of the current and voltage 
curves for each of the time increments be plotted to a scale reduced 



700 


























































































600 












KILOVOLT AMPERE AND KILOWATTTIME CURVES 
ALTERNATING CURRENT SINGLE PHASE MOTORS 








/ 














^■500 


/\ 












































/ 


\ 












































-gioo 

cs 


/ 














































f 


V 


V 








































j^300 






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s 












































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. 








K.V. A. 






































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200 










K.W. 






















































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Coast 






Brake Sta. 
^top., Stop 







4 





8 





1^ 





16 





2C 
T 


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ime 


24 
in 



Sec 


26 
ond 


SO 
s 


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>0 


36 


»0 


4C 


0' 


4- 


10 



Fig. 25. 

in the ratio of 1000 to one, a kilovolt-ampere curve results which 
is quite as useful in determining substation and distribution sys- 
tem requirements as the kilowatt-time curve. Fig. 25 illustrates 
such a kilovolt-ampere curve for a proposed interurban line 
operating 72 ton, 2 car trains, made up of a 44 ton motor car 
and a 24 ton trailer with rotative weight of 4 tons, equipped with 
four 125 h. p., 200 volt, 25 cycle single phase alternating current 
series motors with a 2.33 gear ratio. 

Whereas the kilovolt-ampere time curve is of great value as 
explained above, it is usually necessary to know the actual power 



70 ELECTRIC RAILWAY ENGINEERING. 

consumption expressed in kilowatts at any time during the run. 
This is rendered possible by plotting the kilowatt-time curve, 
Fig. 25, which is related to the kilovolt-ampere curve at any in- 
stant by the expression 

Kilowatts = Kilovolt-amperes x power factor (47) 

Reference to Fig. 99, will show that the power factor of an 
alternating current railway motor varies with the current. In 
order to fix accurately a point on the kilowatt time curve of Fig. 
25, therefore, it is necessary to select a given instant of time, find 
the current in the motor at that instant from the current-time 
curve, determine the corresponding power factor from the motor 
characteristic curve and substitute in equation (47). In many 
cases, however, it will be found sufficiently accurate to assume an 
average power factor for the entire curve with the possible excep- 
tion of the starting value which is usually considerably lower than 
the average operating power factor. 

The area enclosed by a kilowatt-time curve is a measure of the 
energy consumed by the car or train during the run, thus, 

Area of diagram 
E = ^ (48) 

3600 

Area of diagram X1000X5280 

Ei = ~ — —^ (49) 

3600 Wb 

where 

E = Energy in kilowatt hours. 

El = Energy in watt hours per ton mile. 

W = Weight of car or train in tons. 

S = Length of run from station to station in feet. 

If this energy be expressed in kilowatt hours (E) it will be 
found to be in convenient form for calculating substation demands, 
while if expressed in "watt hours per ton mile" (E^) it will be 
found useful in comparing various runs with different types of 
equipment and under different service conditions, since it has 
become customary to express the results of power-time curve 
calculations for the purpose of simplicity in terms of this unit. 



CHAPTER IX. 

Speed Distance, Current and Power Curves 
(Concrete Examples). 

In order that the use of the formulae and the method of plotting 
curves outlined in the previous chapters may be thoroughly under- 
stood, a typical concrete problem will be considered. Although 
this particular case has been considered because of its rather 
exceptional changes in grade, involving the most difficult phase 
of the problem, the curves will first be plotted using the distances 
listed in Table VI,- but assuming the track a level tangent. Com- 
parative curves will later be calculated and plotted to illustrate 
the effect of grades. 

table vi. 

Distances and Grades of Typical Run. 



Street crossings. 


Grade (per cent.). 


Distance from last 
stop (feet). 


Distance from 
start (feet). 


A to B 


o.o 
6.0 

2 .0 

05 

1 .0 


600 
880 
400 
320 
1240 
760 


600 


B to C 


1480 
1880 
2200 


C to D 

D to E 


E to F 


3440 
4200 


F to G 



A 25 ton interurban car, equipped with four Westinghouse No. 
56, 50 h. p., d. c. railway motors and series parallel control, is 
to be operated over this road at a schedule speed of 18 m. p. h. 
The characteristics of this type of motor are found in Fig. 13. 

The initial constant acceleration will be assumed as i . 25 m. p. h. 
p. s. which is a fairly representative figure in electric railway 
practice. 

71 



72 ELECTRIC RAILWAY ENGINEERING. 

A force of loo lb. per ton will be considered as the necessary 
tractive effort to overcome the inertia of both translation and 
rotation in accelerating the car at a rate of i m. p. h. p. s. 
The resistance curves found in Fig. 17 are plotted for a car of this 
weight and will therefore be used in this problem. 

The values which must be substituted for the symbols listed in 
Chapter VII, page 59, are therefore as follows: 

p = i25. 
A=i.25. 

V = i8. 

S = 42oo. 

W=2S. , 

n=4. 

W, = 6.2S. 

Using formula (36) the time of run is 

4200 

T= — — = 1=59 seconds. 

18x1.467 ^^ 

In order to substitute in formula (37) for gross tractive effort 
the value of train resistance (f) must be approximated. This may 
be done sufficiently accurately by selecting the value from Fig. 17 
corresponding to the average speed which must be assumed for 
the constant acceleration period. 

Taking this average speed at 10 m. p. h. (f) = ii lb. per ton. 
From equation (37) 

P = (125 + 11) =136 lb. per ton. 

The gross tractive effort is therefore: 

T.E. = 6.25x 136 = 850 lb. (39) 

Referring to the characteristic curves of this motor, Fig. 13, the 
current and speed for this tractive effort are : 

1 = 84 amp. 

V = 20.4 m. p. h. 

The average speed from the start is therefore 10.2 m. p. h. 
which proves the assumption of 10 m. p. h. used in obtaining the 
value of train resistance (f) was sufficiently accurate. Had this 
assumption been much in error a corrected calculation of tractive 
effort should have been made. 



SPEED DISTANCE, CURRENT AND POWER CURVES. 73 

The time required for the period of constant acceleration is 
calculated from formula (40) 

20.4 
t = = 16, ^ seconds. 

1-25 ^ 

The line (Ob'), Fig. 21, may now be plotted. 
The corresponding distance covered is 

20.4 

s = + X 1.467 X 16.3 = 244 ft. ' (46) 

2 

This determines one point (n') on the distance curve. 

In order to determine the first point (b") on the curved portion 
of the acceleration diagram, an increment of speed must be 
assumed. 

Let dv = 5 m. p. h. or v +dv = 25 . 4 m. p. h. 
The gross tractive effort on the characteristic curve corresponding 
to 25.4 m. p. h. is 

T.E.=40olb. 

The average speed for this increment being 22.9 the new value 
of train resistance (f) will be found from the resistance curves 
to be 

f' = i5 lb. per ton 

The new value of net tractive effort is therefore 

400 
p' = ^-^-i5=49 lb. per ton. (41) 

The corresponding value of acceleration is 
*, 49 



XI .25 = 0.49 m. p. h. p. s. (42) 



125 

dt= — =10.2 sec. (43) 

.49 

The coordinates of the point (b'^) are therefore : 

(V + dv) = 25.4 m. p. h. and (t+dt) = 26.5 sec. 

The corresponding point on the distance curve is found as follows 

20.4+25.4 

(jg^ _x 1.467 X 10.2 = 342 ft. (46) 

2 



s = 244 +342 = 586 ft. from start. 



74 



ELECTRIC RAILWAY ENGINEERING. 



Neg ecting the grade which is encountered at a distance of 14 
ft. beyond the above point and continuing the above ''step by 
step" method the values listed in Table VII may be determined 
and the acceleration portion of the diagram plotted to the point 
(i') where the speed becomes constant. 

TABLE VII. 
Calculated Data, Speed, and Distance Time Curves. 



dv 


V + dv . 


dt 


t + dt 


ds 


s + ds 


5 


25-4 


10.2 


26.5 


342 


586 


3 


28.4 


10.7 


37-2 


421 


1007 


3 


314 


22 .2 


59-4 


974 


1 98 1 


3 


34-4 


49.1 


108.5 


2370 


4351 



As uming the total braking resistance including train resistance 
b = 150 lb. per ton which, of course, will produce a deceleration of 
1.5 m. p. h. p. s., a straight line may be drawn back from 
T = 159 sec. with the above deceleration as its slope. Such a line 
is Tr', Fig. 21. 

The train resistance during coasting should be selected as 
nearly as possible to the value which, on the train resistance 
curves (Fig. 17), corresponds to the average speed expected during 
the coasting period. The value of 15 lb. per ton is often taken 
arbitrarily to represent this resistance and will therefore be used 
in this problem. Since this corresponds to a deceleration of o. 15 
m. p. h. p. s., a line with this slope is drawn in the position 
(f'k), cutting the braking line at point k'. 

If the area of the diagram (Ob'b^'f^k'T) be measured with the 
planimeter it will be found to contain approximately 123 section 
squares. With the particular scales of speed and time used each 
square is equivalent to a distance of 36.6 ft. The diagram 
therefore represents a distance of 123 x 36.6 ft. =4500 ft. which 
is greater than the length of the run. The coasting line must 
therefore be redrawn parallel with itself but starting with a lower 
initial speed until, by the "cut and try" method, until the area 
of the diagram is found to correspond to the length of the 



SPEED DISTANCE, CURRENT AND POWER CURVES. 75 

run in feet. Such a d'agram is that bounded by the lines 
(Ob'b''l'm'T), Fig. 21. If the true coasting resistance be now 
determined it will be found to be 13.5. The assumption of 15 
was therefore conservative. 

The distance time curve will be of value in approximating the 
correct area of the diagram. The values of distance from Table 
VII plotted against time would produce the curve of distance 
covered by the car if it were to be allowed to reach constant speed. 
However, since the power is shut off and coasting begun at a speed 
of 27 . 5 m. p. h., a new distance curve must be determined beyond 
this point. 

The distance corresponding to point (P) is found as follows: 

27.5 + 25.4 

Avg. V = = 26.5 m. p. h. 

2 

t = 33 sec. 

ds = 26.5 X 1.467 X (33-26. 5) = 252 ft. (46) 

s = 586+ 252 = 838 ft. from start. 

Continuing the calculations of distance corresponding to the 
coasting and braking portions of the diagram the distance time 
curve (On'n'^p^) is determined which at 159 seconds checks very 
closely the length of the run. 

Speed and Distance Curves for Actual Grades. — If the 
actual grades listed in Table VI be considered, the curves take 
quite a different and more complex form. Since it was found in 
the previous calculations that the point (b'') corresponded to a 
distance but 14 ft. short of (B), Table VI, where the grade 
changes to 6 per cent, it will introduce little error and simplify 
the calculations considerably to consider the grade beginn'ng at 
this point. 

Since the 6 per cent, grade will cause an immediate reduction in 
speed, a decrement of 3 m. p. h. will be assumed. 

dv = 3 m. p. h. V = 22.4 m. p. h. Avg. V=23.9 m. p. h. 
(f'^) at 23 . 9 m. p. h. = 1 5 . 4 lb. per ton. 
T.E. at 22.4 m. p. h. = 600 lb. 

600 

p//_^ -15.4-120= -39.4 lb. (41) 

6.25 



76 ELECTRIC RAILWAY ENGINEERING. 

Deceleration = 0.394 m. p. h. p. s. (42) 

(it = = 7.6 sec. 

.394 

New point on curve has coordinates as follows: 

V=22.4 m. p. h. t = 26. 5 + 7.6 = 34. 1 sec. 

ds = 23. 9 X 1.467 X 7.6 = 266 ft. (46) 

s = 586+ 266 = 852 ft. 

The corresponding point on the new distance time curve is there- 
fore determined. 

Following this method, being careful to observe every change 
of grade at its correct distance from the start, the rather irregular 
curve (Ob'b'^s''F^m''T) results. If the distance corresponding to 
each of the steps assumed for the speed time curve be calculated 
the distance time curve (On'n''p'') may be plotted. If it be 

ds 
remembered that the slope of the distance time curve — repre- 
sents speed, the effect of grades in reducing speed will readily be 
detected if the two distance curves are compared. 

While the amounts of coasting in both of the speed time curves 
considered are very generous, the effects of grades both in reducing 
the possible coasting and in increasing the coasting deceleration 
in the second case are marked. If stops were necessary in this 
distance the coasting periods would be greatly shortened and 
possibly eliminated if the same schedule speed were maintained. 

Current and Power Curves. — The gross tractive effort during 
the constant acceleration period (Oa'), Fig. 21, was found to be 
850 lb. which required a current value per motor of 84 amperes. 
During the first half of this same period plotted to the same scale 
on Fig. 23 therefore, the current per pair of motors in a four motor 
equipment is 84 amperes while the current per car is 168 amperes. 
In the second or parallel half of the period, however, the corre- 
sponding values' of current are 168 and 336 amperes respectively. 
In determining the other points on the current curve such as the 
current after 20 seconds have elapsed, for example, it is found 
from Fig. 21 that the speed is 22 . 5 m. p. h. Referring to the speed 
characteristic, Fig. 13, the corresponding current is found to be 64 
amperes per motor or 256 amperes per car since all four motors 



SPEED DISTANCE, CURRENT AND POWER CURVES. 77 

are now operating in parallel. This value is plotted against a 
time abscissa of 20 sec. on Fig. 23. Following out this 
method the current required for operating the car over the level 
track will be represented by curve (OCfkb'^lq'), Fig. 23, while the 
corresponding current with the actual grades introduced is 
illustrated in curve (OCfkb^'mnq'''). 

As an average voltage of 500 volts has been assumed on this 
road the ordinates of the two similar curves of Fig. 24 are 500 
times those of Fig. 23 reduced to the convenient scale of kilowatts. 
If these curves be compared with the speed time curve, Fig. 21, 
the ncreased values of power required as the car enters the grades 
will be noted. 

The areas of the two kilowatt time diagrams, Fig. 24, are 3960 
and 12,100 kilowatt seconds respectively. Applying formula (48) 
the energy required by the level run is, 

3960 
E = -; — = 1.1 kw. hr. (48) 

3000 

while that of a run involving the existing grades is, 

1 2 100 
£ = -"- = 3.36 kw.hr. (48) 

3000 

The energy consumptions for the two runs expressed in watt 

hours per ton mile are, 

3960 X 1000 X 5280 

El = -^ ^ = 55 . 3 w. hr. /ton mile. (49) 

3600 X 25 X 4200 

12100 X 1000 X 5280 

E', = = 169 w. hr. /ton mile. (49) 

3600 X 25 X 4200 

Since the rolling stock and equipment in this case are rather 
lighter than that of average interurban practice the value of 55 . 3 
watt hours per ton mile for the level track is rather a low figure 
while the steep grades in the latter case render the figure 169 for 
E'l rather above the average. The very fact, however, that these 
values of energy vary over so wide a range illustrates the marked 
effects which may be attributed to local conditions and emphasizes 
the necessity of a complete and detailed study of each proposed 
road before accurate estimates can be made of its cost of construc- 
tion or dependable conclusions drawn regarding the advisability 
of its installation. 



CHAPTER X. 
Speed Time Curves (Straight Line). 

The method of plotting speed time curves outlined in the 
previous chapter is most desirable for final calculations where 
considerable accuracy is necessary. For preliminary approxi- 
mate results, however, it is not necessary to go to this refinement 
and the so-called "straight line " speed time curve described below 
is therefore used. 















































COMPARISON OF SPEED - TIME CURVES 








30 








































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30 



40 



60 



80 100 
Seconds 

Fig. 26. 



130 



140 160 



In Fig. 26 will be found reproduced the speed time curve 
(Oabcd) calculated in Chapter IX for a straight level track, Fig. 
21. If, now, the time (Od) and the distance, represented by the 
area (Oabcd), are kept constant and the acceleration be assumed 
constant, i.e., the acceleration portion of the figure a straight 
line, the diagram (Oaec'd) may be drawn with the same area and 
with the average assumed coasting and braking decelerations of 
0.15 m. p. h. p. s. and 1.5 m. p. h. p. s. respectively. Such 

78 



SPEED TIME CURVES. 



79 



a chart, although it may vary considerably in some details from 
the more accurately drawn curve previously considered, is exten- 
sively used for rapid calculations of possible schedules for a given 
road and for the rough determinations of required equipment and 
preliminary estimates. 

Granted that the straight line diagram is sufficiently accurate 
for most practical purposes, an unlimited number of similar speed 
time diagrams may be plotted for the same distance and time by 
varying the rate of acceleration but with constant coasting and 
braking decelerations. Such a series of diagrams for a i mile 
run in 120 sec. appears in Fig. 27,^ in which (OBC) represents 



60 



u 40 
3 



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:J0 40 60 80 100 \Zd 

Seconds 

Pjq 27. — Typical Speed Time Curves. (Varying rates of Acceleration.) 



a run with no coasting and therefore the lowest possible rate of 
acceleration, while the other extreme case, which is of course 
theoretical only, is represented with an acceleration (OA) infi- 
nitely great. Between these two limiting values there are a num- 
ber of possible selections to be made, the gross tractive efforts 
listed on the chart including the net effort necessary for accelera- 
tion plus the 15 lb. per ton train resistance assumed for all 
diagrams. It should be noted that the dotted fine (AB) is the 
locus of maximum speeds for all diagrams. 

Furthermore, if the distance still remain constant at i mile and 
the time for the entire run be varied the more complete chart, 
Fig. 28,^ results,which is made up of a series of charts like Fig. 27, 



^ Taken from "Electric Traction," by A. H. Armstrong. 



8o 



ELECTRIC RAILWAY ENGINEERING. 



each having its own acceleration variations for a fixed distance 
and time. The dotted curve of Fig. 28 represents the locus of 
maximum speeds necessary to cover the distance of i mile 
in any given time represented as an abscissa. For example, 
if it be desired to cover the mile run in 150 sec, the braking line 
terminating at 150 sec, shows the maximum speed with any 
acceleration to be 48 m. p. h. corresponding to a gross tractive 
effort of 51.2 lb. per ton. If other rates of acceleration are pos- 
sible the particular chart designated by the point 51.2 may be 
treated as outlined in Fig. 27. 



100 



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60 120 180 210 

Seconds 

Fig. 28. — General Speed Time Curves. 



These charts are of little use, however, unless readily applicable 
to various lengths of run. Such application may be made in the 
following manner. 

It can be readily proved geometrically that the ratio of the alti- 
tudes or bases of two similar trapezoids is that of the square root 
of their areas. The speed-time diagrams which have been con- 
sidered in this chapter are trapezoids with altitudes representing 
maximum speeds, bases representing time, and therefore with 
areas expressed in terms of distance. If the length of run be 
changed, keeping the same acceleration and coasting and braking 



SPEED TIME CURVES. 8 1 

decelerations, the diagrams for the two lengths of run will remain 
similar and the following formulae may be derived for the calcula- 
tion of maximum speed and time. 

T = Schedule time for original run. 
T' = Schedule time for new run. 
S = Distance of original run. 
S' = Distance of new run. 
V^ = Maximum speed of original run. 
V'jj^ = Maximum speed of new run. 

>|, (50) 



m O 



v„ 'Vs 



(51) 



As an illustration of the use of these formulae, it will be assumed 
that the speed-time diagram is desired for a run one-half the 
length of that considered in the previous chapter (2100 ft.), 
Fig. 26, with the same rate of acceleration, coasting, and braking. 
From the diagram the following values may be scaled : 

T=(Od) = i59sec. 
V^=(ef)=28.5m. p. h. 
S=42oo ft. 

Substituting in equations (50) and (51) 

T' = i59\/ov5 = ii2.4sec. (50) 

V'na=28.s\/o.5 = 2o.i m. p. h. (51) 

Plotting these values, the diagram (Oe'cM') results and there- 
fore represents fairly accurately a speed-time curve for a distance 
of 2100 ft. with a minimum of labor involved in its determination. 

Energy Calculations. — As the acceleration was assumed 
constant in the above diagrams, it is usually not sufficiently 
accurate to derive from them the current and kilowatt-time curves 
as was done in Chapters VIII and IX. The energy required for 
the run may be closely approximated, however, by the following 
method, which may also be used to advantage as a check on the 
power-time curves when the latter are plotted by the "step by 
step" method. 
6 



82 ELECTRIC RAILWAY ENGINEERING. 

Assume the following nomenclature. 

V = Average speed in m. p. h. 

V^ = Initial coasting speed in m. p. h. 

V^ = Initial braking speed in m. p. h. 

r = Total train resistance in lb. per ton including (f ±g + c). 

Ej = Energy in watt hours per ton mile. 

2000W 

m = Mass of car = . 

g 
b = Braking force at periphery of car wheel in lb. per ton. 

S^ = Distance travelled from beginning of coasting period to 

stop with no braking. 

S^ = Distance travelled from beginning of braking period to 

stop. 

t^ =Time of coasting in sec. 

t^ =Time of braking in sec. 

V X 5280 X r X 746 

Ei = — T-j — = i-99r (52) 

60 X 33000 V 

This may be considered with little error to be (2 r). 

This represents in simple form the net power at the wheels of 
the car. To obtain the gross input to motors this must be divided 
by the efficiency of the motors with gears included. 

Energy During the Braking Period. — Furthermore, it should 
be noted that neither equation (52) nor the formulae of Chapter 
VIII include the power required to stop the car. To determine 
this power exerted during the braking period, proceed as follows : 

m(VbXi.467)2 
e = ^ (53) 

but 

e = S, (b + r) (54) 

therefore 

2000 W (1.467 Vu)^ 
WSb (b+r) = ^ g (55) 

The power during the braking period is therefore 

Ft. lb. per min. 60 WS^ (b + r) 

H. p. = = 

33000 33000 tb 



SPEED TIME CURVES. S^ 

or simplified 

60 X 2000 W (1.467 Vb)' WV\ 

H. p. = =0.121 (56) 

32.2 X 2 X 33000 tb % 

Coasting Energy and Train Resistance. — If, however, the 
above reasoning be applied to the results of a coasting test in 
which the car or train is allowed to coast to a standstill from 
various initial speeds the train resistance may be calculated thus 



2000 W (1.467 VJ^ 

WSer = : / ^' (57) 

2 g 

whence V^^ 

r = 66.8— ^ (58) 

By thus combining the straight line speed-time charts with the 
calculation of energy from the above formulae, a rapid although 
approximate method of calculating train performance is provided 
which will be found of great convenience. 



PART II. 

POWER GENERATION AND DISTRIBUTION. 



CHAPTER I. • 

Substation and Power Station Load Curves. 

Whereas the previous chapters have been devoted to the oper- 
ation of cars and trains with the ultimate object of determining 
the demands which they may make upon the power distribution 
system, it is now necessary to study the combination of individual 
train demands and their connection with the average and maxi- 
mum loads on the substation and power station. 

The load curves of substation and power station have been 
treated simultaneously for the reason that the substation of a 
large urban railroad or a relatively long interurban line acts as a 
source of power for the surrounding distribution system and 
therefore, as far as the determination of station output and 
capacity are concerned, it matters little whether the machines 
supplying the cars are in turn furnished with electrical power 
over a high tension transmission line or whether they are driven 
by engines or turbines. 

The most convenient units in which quickly to express the 
power demands of a train were found to be ''watt hours per ton 
mile." This demand was shown to vary greatly with schedule 
speed, weight of cars, condition and profile of track, length of 
run, etc. It is clear, therefore, that except in very exceptional 
cases, a single value of energy cannot be applied for the entire 
length of an interurban run from terminal to terminal. Occa- 
sionally, however, with a straight level right of way, with fairly 
constant schedule speed throughout the run and with all cars of 
about the same size and weight, an average value of energy may 
be used for all cars for the entire run and the average substation 
demand for the day determined as follows : 

E = Energy in kilowatt hours. 

El = Energy of car in watt hours per ton mile. 

W = Weight of car in tons. 

Sg = Length of section supplied by station in miles. 

87 



S8 ELECTRIC RAILWAY ENGINEERING. 

N = Number of trips in both directions over section per day 

determined from graphical train schedule. 
Eff . = Efficiency of distribution system in per cent. 

The energy demand upon the substation in a day is therefore 

NWEjS, 
^ = 1000 xEff. (59) 

The average load on the station in kilowatts during the day is 

E 

^ = ^ ' J- (M 

Hours operation per day 

If it were not for the excessive current taken during the acceler- 
ation period as compared with the full speed running current, 
the maximum load on the station might be determined by multi- 
plying the average power required per car (average ordinate of 
the kilowatt-time diagram, Fig. 24) by the maximum number of 
cars operating upon a single substation section at any one time. 
This method will usually give too low a maximum demand, 
however, and it is therefore necessary to find the maximum 
number of cars starting simultaneously on a single section. For 
such cars the maximum, ordinate of the power time curve. Fig. 24, 
must be used together with the average ordinate of the curves of 
such other cars as may be running upon the section at the same 
time. To correctly determine the number of cars starting at any 
one time a great deal of judgment and knowledge of local con- 
ditions is necessary in addition to a familiarity with the train, 
schedule. If there be a siding located on the section it is safe 
to assume at least two cars starting simultaneously. 

While this method of determining average and maximum loads 
upon a substation has been successfully used in practice, especially 
where preliminary estimates only were involved and the runs 
between stations on a given section were quite similar in all 
respects, the more detailed method outlined below is usually 
finally adopted. 

A series of speed, current, and kilowatt-time curves are plotted 
for the entire road, one curve for each run between stations. If 
more than one class of service, such as local, limited, freight, etc., 
is proposed, a similar series of curves must be plotted for each. 



SUBSTATION AND POWER STATION LOAD CURVES. 



89 



From the kilowatt- time curves it is possible to scale off the area 
representing the energy taken by the car or train during any 
particular interval of time throughout the run. The combined 
areas of all these curves may readily be expressed in terms of 
kilowatt hours per run or, better, the portion of the run which is 
shown by the time abscissa and train schedule to be on a given 
substation section may be thus treated. It is only necessary, there- 
fore, to integrate all types of runs throughout the day on a given 
section in order to obtain the total energy and average load on 
the station in a similar manner to that of equations (59) and (60). 



700 




















SUBSTATION LOAD CURVE 
































































600 
















nil 




11 












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f 


n 




























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il II 




1 












ii! 




1 

1 




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--- 


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1 


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Jl.. 


— 


— 


— 


_.. 


.... 


J'.i . 


■-' — 


.-.1 




1 







— 




500 






















































^400 


































































































2 
2 300 








































i 


























































300 
















1 




■1 




















p 












































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li 




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:00 8:00 
A.M. 



10:00 



12:00 2:00 
P.M. 



4:00 6:00 

Fig. 29. 



:00 



10:00 



12:00 
A.M. 



The problem may be carried one step farther if necessary and 
the ordinates of kilowatt-time diagrams of all trains on the section 
for each increment of time added together to form the most 
accurate load diagram which it is possible to predetermine for 
the substation. 

Many modifications of these two methods will present them- 
selves to the engineer as best fitted to local conditions and to the 
degree of accuracy required. Fig. 29, for example, is a load 
diagram made up of rectangular areas, each representing the 
average kilowatt-hour demand of all cars on one of the 12 
mile substation sections of an existing interurban road at a given 
hour of the day. The average load on the station found by 
taking the average ordinate of this curve for the day is 69.3 kw.. 



90 ELECTRIC RAILWAY ENGINEERING. 

while the maximum demand from the upper curve plotted with 
reference to the possible number of cars starting simultaneously 
on the section is 655 kw. 

In plotting station load curves by whatever method, it must be 
remembered that most roads have not only the daily fluctuations 
of load which will be shown by the peaks of the load time curve 
plotted for a single day, but there is usually considerable difference 
between the load curves for the various seasons of year, even the 
train schedule being changed for one of less headway in the 
summer season. This fact, together with the possibility of 
sudden daily demands due to special attractions along the line of 
the interurban road, especially upon holidays, must be given 
careful attention in applying load curves to the location and 
design of substations and power stations. 

Load Factor. — The "load factor" of a station for a given 
period has been defined as the ratio 

Average power demand 
Maximum power demand 

although it is often considered as the ratio of average demand to 
station capacity. The load factor, as determined from the load 
curve of the substation in this particular case is therefore, 

69.3 
-^ = 10.6% (61) 

While a low load factor is to be avoided if possible, since it 
follows that such a factor involves the use of relatively large 
station equipment operating at light and therefore low efficiency 
loads; yet in interurban practice where the traffic is relatively 
light and the trains few in number but demanding large amounts 
of power, as compared with the city systems, it is hardly possible 
to improve conditions of load factor to any great extent over the 
particular case which has been used as an illustration. 



CHAPTER II. 
Distribution System. 

The circuit which the propulsion current for a car follows 
extends from the feeder panel of the substation over the out-going 
feeders and trolley to the car motors, thence through the rails 
back to the substation switchboard or, in some cases, directly to 
the negative terminal of the converter. The voltage at the sub- 
station is maintained constant, usually at 550 or 600 volts. The 
current flowing over the above circuit causes a drop of potential 
in proportion to the resistance of the entire circuit in accordance 
with Ohm's law. This fall of potential subtracted from the 
substation potential determines the voltage at the car. As the 
latter voltage should be as high and as constant as possible if 
good service is to be maintained, it follows that the resistance of 
the feeders and track return should be carefully proportioned. 
The latter will be discussed in detail under the subject of " Bonds 
and Bonding^, " Chapter VI, while this chapter will be devoted to 
the study of the overhead trolley and feeder system. 

On interurban roads and often in the city systems the trolley 
is sectionalized by the introduction of circuit breakers in the 
trolley wire which insulate one section from another. Cables 
from either side of the breaker are carried to a pole switch by 
means of which the sections may be connected together if neces- 
sary. Each section is generally supplied with power from a 
single substation through the agency of feeders paralleling the 
trolley for a portion of its length. The trolley wire itself for 
mechanical reasons is usually from No. 00 to No. 0000 B & S 
gauge hard drawn copper and is often installed double with 
wires about 6 in. apart but electrically connected at every 
hanger. Where the current required is considerable this prac- 
tice is very commendable, for the second trolley replaces an equal 
amount of copper which would otherwise be installed in the 
insulated feeder and, what is of greater consequence, it eliminates 

91 



92 ELECTRIC RAILWAY ENGINEERING. 

all overload switches and frogs in the trolley wire at sidings, the 
wires being spread as the tracks are separated, the car trolley 
always remaining on the right wire. With the size of trolley 
given, together with a well bonded track of known weight and 
resistance, the problem resolves itself into one of feeder design. 

Since the problem is necessarily treated differently for inter- 
urban and urban roads the former will be first considered. The 
minimum permissible voltage at the car under the worst condi- 
tions must first be assumed. While this voltage drops at times 
in interurban practice to 250 volts, a value of at least 350 volts 



r^l I II I I Feeder Kn 

L I I I I I ' ' I I I I L J 



gX ^X . Trolley 

I h — h ^ 



Fig. 30. — Continuous Feeder Distribution. 

should be used. This allows 250 volts drop in the distribution 
system under maximum trafiic conditions. Reference to the 
train schedule will determine this maximum condition which 
usually involves two cars starting simultaneously and possibly 
others operating on the same section. Assuming the simplest 
form of distribution, Fig. 30, with the feeder paralleling the trol- 
ley for the entire length of the section and tapping into it suf- 
ficiently often so that they may be considered as one wire of 
large section, the following solution may be outlined. 

e = Permissible voltage drop. 
1 = One-half length of section in feet. 
lj = Distance of car (A) in feet. 
l2= Distance of two cars at (B) in feet. 
I^ = Current taken by one car at (A) . 
1^ = Current taken by two cars at (B). 
R^ = Resistance per ft. of track (two rails). 
Rp^= Combined resistance per ft. of feeder and trolley. 
r = Resistance of copper per mil. ft. 

As in mechanics the combined loads I^ and I^, determined 
from the current-time curve, may be considered as acting through 



DISTRIBUTION SYSTEM. 



93 



the equivalent distance (Ig) of the center of gravity of load from 
the substation where 



Volts drop in track (e„) = lgR^(l4+ 13) 
Allowable drop in feeder and trolley 

e_=e-lgR^(I^+IJ 



'FT 



R„ = 



(I.+ Ib)1, 
Combined area of feeder and trolley in 

circular mils 



rl 



R 



(62) 
(63) 
(64) 
(65) 

(66) 



FT 



Having determined the necessary combined area of feeder and 
trolley from equation (66), or from the wire tables, the known 
area of the trolley wire or wires may be subtracted and the neces- 
sary size of feeder remains. 

Assuming for illustration two cars whose current-time curves 
are represented in Fig. 23 starting 3 miles from the sub- 
station and a similar car running at full speed 2 miles from 
station. The trolley consists of two No. 4/0 B & S wires and 
the track is of 70 lb. rail with 9 in. bonds equivalent to 
one-half the rails in conductivity. The resistance of copper may 
be taken as 10.6 ohms per mil. ft. 

Armstrong gives the resistance of third rails and track rails 
with the above bonding in the following table. 

TABLE VIII. 
Resistance of Third Rail and Track. 



Wt. of rail per yd. 40 

1 
1 


50 


60 


70 


80 


90 


100 


no 


Third rail resistance, ohms per . 093 

mile. 
Two track rails resistance, ohms . 066 

per mile. 


.074 
•053 


.062 
.044 


•053 
.038 


.046 .042 
•033 -033 


.038 
.027 


•034 
.024 



94 ELECTRIC RAILWAY ENGINEERING. 

I^ from Fig. 23=^672 amp. 

Ig=i6o amp. 

5280(672 X 3 + 160 X 2) 

Lp = T —=14,800 ft. = 2.8 mi. (62) 

832 

Volts drop in track =832 x .038 x 2.8 = 88.5 volts (63) 

Allowable drop in feeder and trolley = 161. 5 volts (64) 

161. 5 
R^a-=;; ^ — =.00001^1 or .01 ^i ohms per 1000 ft. 

^^ 832 X 14800 o o r 

Corresponding area from wire table = 800,000 cm. 
Two 4/0 trolley wires = 423,200 cm. 
Feeder section = 376,800 cm. 

Either a standard 350,000 or 400,000 cm. cable might be chosen. 
If, in place of isolated sections of trolley, the wires be continu- 
ous from terminal to terminal and the substations connected in 

*i ■ +2 

A 

X 



h 1-^ >f -l-^ ^ 

Fig. 31. — Division of Current between Substations. 

parallel with one another between trolley and rail, such a prob- 
lem as that assumed above would involve the determination of the 
portion of the current per car which was supplied from each of 
the two adjacent stations. Here again the principles of mechanics 
may be applied as illustrated in Fig. 31 where (A) is a car at 
distances (1^) and (\^) from substations No. i and No. 2 respect- 
ively. If the car is drawing a current (IJ it may be safely 
assumed that its current demand on substation No. i is 

I. = f^ (67) 

while the current taken from No. 2 is 

IJa 

With this understanding a problem in feeder calculation 
similar to the above offers no additional difficulties. 

Each half of the section in Fig. 30 was considered independ- 
ently of the other for the reason that the feeders and trolleys of 



DISTRIBUTION SYSTEM. 95 

the two halves of the section are in parallel and therefore the 
voltage drop in one does not affect the other. The solution of 
a problem with the substation located at the end of the section 
would therefore be treated in a similar manner. 

In many cases, however, feeders are tapped into the trolley at 
infrequent points, thus forming a network whose calculation is 
slightly more involved. Such a condition is illustrated in Fig. 32. 
The feeder is tapped to the trolley at the two points (a) and (b) 
at distances from the station of (1) and (IJ respectively. Two 
cars are starting at (B) at a distance (1,) from the station with 
total current {IJ. 

Volts drop in track = I3R^1 2 (69) 

Allowable drop in feeder and trolley ep^ = e — IgR^lj (70) 



r 



a qX 



h 



Trolley 



Fig. 32. — Feeders with Infrequent Taps. 

In any branched circuit problem such as this it is always most 
convenient to make use of Kirchoff's laws which may be stated 
as follows: 

First, "At any point in a circuit, the sum of the currents 
directed toward the point is equal to the sum of those directed 
away from it." 

Second, " In any closed circuit the algebraic sum of the (IR) 
drops is equal to that of the (e. m. f. s.)." 

While in this simple problem it is obvious without stating such 
a law that the current entering the cars at (B) is the sum of the 
two currents arriving at (B) by the two paths from (a) and (b) 
respectively and also that the drop in potential between (B) and 
(b) must be the same by either path, yet in complicated networks, 
especially in city streets, the statement of Kirchoff's laws in this 
form is most acceptable. 

The resistance from (b) to (B) direct is that of (I2-I1) ft. of 
trolley or 

RbB=Rw(U-ii) (71) 



96 ELECTRIC RAILWAY ENGINEERING. 

if (R^) represents the resistance of the trolley per foot. The 
corresponding resistance by path (a) is 

R,3=R„(i-g+R,(i-g (72) 

with (Rp) representing resistance of feeder per foot. The currents 
in the two branches may now be calculated from the two equa- 
tions 

lB = Ia+Ib (73) 






(74) 



With the current in each branch known, the fall of potential 
between point (b) and the car (B) may be determined from either 
of the equations 

eaB = Ia(RaB+Rba) (75) 

ebB^IbRbB (76) 

That these two drops in voltage are identical will be shown more 
conclusively by substituting in (75) the value of current (I J 
obtained from equation (74). 

As the total current (IJ is flowing through the feeder between 
(b) and (S) the additional drop over this distance is 

^bs^-'^b^F^l 

The total drop in the overhead conductors between substation 
and car is therefore, 

e, = IbRbB+IbR.li (77) 

If the feeder had been tapped into the trolley at the substation 
(S) in addition to the other taps a second network would have 
been added to the calculation, but the method of solution would 
not have been changed. In fact, any network may be readily 
solved with the use of Kirchoff's laws if taken step by step. 

City Systems. — The principal difference between the calcula- 
tion of urban and interurban feeder systems is that in the former 
it is necessary to consider a large number of cars per section, each 
drawing an average current which may be readily determined 
from their relative current-time curves or from actual tests with 
meters on the car if the road is already in operation. Such 
sections may ordinarily be considered as uniformly loaded 
without serious error. 



DISTRIBUTION SYSTEM 97 

Such a section, represented by Fig. ;^^, may be treated as a 
uniformly loaded beam in mechanics and in place of using the 
individual values of current taken by each car at a, b, c, etc., 
the total current of all cars on the section combined may be con- 
sidered as being taken from the mid-point, distant I/2 ft. from 
the station. The correctness of this method may be readily 
jJroved by integrating the voltage drops (ir dl) between the 
limits of zero and the length of the line (1) where (i) represents 
the current per foot and (r) the resistance per foot respectively. 



>rv^4'Y'T4'YVYvVT 



a b c <J 



Trolley 
Fig. ;^2,. — Uniformally Loaded Distiibution Section. 



Having now but the single equivalent current to consider, the 
problem may be solved as in the case of interurban systems 
previously described. 

Although the limiting voltage drop is always the first con- 
sideration in railway feeders, it is well to check the safe carrying 
capacity of the cable selected by the above methods with the 
actual current which is flowing therein, the safe carrying capac- 
ities for open wiring being readily found in any electrical hand- 
book. 

Financial Considerations. — While the foregoing calculations 
will give the proper size of feeder to be installed for a given 
minimum potential at the car, it may be found that because of 
too great an assumed distance between stations or for other 
reasons the cost of the copper is prohibitive. Some consideration 
must therefore be given to the amount of power lost in the distri- 
bution system, and the relation of its annual cost to the interest 
and depreciation on the copper to be installed. 

If the I^R losses be summed up for each portion of the distri- 
bution section or if this same total loss be obtained from the 
product of the squared current by the equivalent resistance of 
the overhead conductors and rail return, the efficiency of the 
7 



98 ELECTRIC RAILWAY ENGINEERING. 

distribution system and the annual cost of power lost in distri- 
bution may be determined from the following equations. 

Power delivered to car 

Effy. Dist. System = - — — -— — (78) 

Power delivered to car+I^R loss 



Cost of power 
Annual cost 121? i^vcc li^ cents per 

of distribu-= ( — x hours per year) x ' kw. hr. at d. c. (79) 

buses of sub- 
station. 



,. , 1000 

tion loss 



Kelvin's law states that the most economical size of feeder 
to install is that in which the annual cost of power loss is equal 
to the interest and depreciation figured on first cost of installa- 
tion. As the annual cost of power loss for a given length of 
feeder and current transmitted will decrease, while the interest 
and depreciation charges will increase as the size of the cable 
increases, curves of these costs plotted with size of cable as 
abscissae will intersect at the most economical size of wire to be 
installed. Such curves plotted for a current of 100 amperes in 
1000 ft. of feeder with interest taken at 6 per cent, and depre- 
ciation at 2 per cent, will be found from Fig. 34 to determine a 
feeder size of 375,000 cm. section for which either the 350,000 
or 400,000 cm. standard size might be selected. The calcula- 
tions from which these curves were plotted involved a cost of 
power of one cent per kilowatt hour and a cost of copper 
installed of 20 cents per pound. 

Since any one of these feeder calculations taken by itself may 
give results which are unfavorable when all requirements of the 
distribution system are considered, it is the duty of the engineer 
to calculate the proper feeder sizes necessary for a satisfactory 
line drop, to check these calculations for carrying capacity and 
by Kelvin's law and then to determine the relative weight to be 
given to the considerations of fall of potential, carrying capacity, 
and relative cost of power loss in the particular system in question. 

High Voltage Direct Current Distribution. — While it will 
be seen in the following chapter that the substation connections 
are somewhat different in the case of the comparatively few roads 
operating with a direct current voltage of 1200 volts on the trolley, 



DISTRIBUTION SYSTEM. 



99 



the distribution system is materially the same as for 600 volts, the 
potential being applied between trolley and rail as before with 
the necessary feeders paralleling. the trolley for a portion of the 
length of the line and tapping into same at points where the 
voltage would otherwise be too low. 

The principal difference between the two systems is the greater 
distance between substations and therefore the fewer substations 



o 
Q 

•255 

c 
o 



d 



50 



ft45 

n 

-dlO 

m35 

2 

-S30 

M 

o 

o 

O lo 

o 
10 



























































KELVIN'S LAW 


























































1 






































<5 


/ 








\ 












.^-^ 


f 


/ 








\ 












.y 


r 












\ 








/ 
















\ 






/ 


















\ 


k 


A 






















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.^ 














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. i 


h£i 


OSS 




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200,000 400,000 600,000 800,000 1,000,000 
Feeder Size in Circular Mils. 



Fig. 



34- 



required. As the distance to which power may be transmitted 
with the same percentage loss and first cost of copper varies 
directly with the distance, it is clear that with 1200 volt supply 
the substations may be double the distance apart; and, although 
the distribution feeders may be longer, they have to transmit but 
one-half the current for a given load, and are therefore but one- 
half the area necessary for 600 volt service. The method of cal- 



lOO 



ELECTRIC RAILWAY ENGINEERING. 



culation of feeder sizes is, however, identical with that explained 
above. 

Single-phase Distribution.-^ With the introduction of rail- 
way equipment designed for operation from a single-phase 
trolley, the distribution system is changed slightly. While the 
trolley and track return are still used, the voltages applied to the 
trolley have been increased to 3300, 6600, or 11,000 volts and in 



^_ _5-5ii_ -^ 



rt-^tiE 



Trausmission Line, 33CO0 Volts 



■2-23/" 



Strand Aluminum Cables 



Equiv. to No. 2 B. & S. Copper 



Catenary Cable -6600 Volts 
^"-7 Strand Extra Strength 
O.H. Steel GalT. 

Trolley Wire, 
COOO Volts 
1 - No. (WOO 




Fig. 35. 



order to render high speed current collection reliable with the 
further advantage of longer spans and better insulation the so- 
called " catenary " construction has been generally adopted. This 
design involves the use of one or two steel messenger wires freely 
suspended in spans of several hundred feet each, with a convenient 
amount of sag, which in turn support the trolley wire by means of 
vertical hangers of varying length spaced about ten feet apart and 



DISTRIBUTION SYSTEM. 



lOI 



SO adjusted that the trolley wire hangs perfectly level. This 
eliminates the usual vertical rise of the trolley pole at supports 
with the accompanying tendency to leave the wire at such points 
when operating at high speed. Such single catenary construction 
on the Chicago, Lake Shore, and South Bend Railway is well illus- 
trated by the typical elevation, Fig. 35, while the more complicated 
but stronger construction used by the N.. Y. N. H. & H. R. R. 
in its New York terminal electrification will be found in Fig. 36. 




Fig. 36. 

With the higher trolley voltages used with this system, the 
substations, if necessary at all, are much farther apart and 
trolley sections usually longer. Upon the shorter roads the 
transmission line and substation may often be eliminated, while 
the possible generation of power at 6600 or 11,000 volts often 
permits the step-up and step-down transformers to be omitted as 
well with a corresponding decrease in first cost of installation and 
maintenance. Three-phase generation is generally adopted 
because of the lower cost and small size of three-phase generators 
as compared with single-phase units. This necessitates balancing 



I02 



ELECTRIC RAILWAY ENGINEERING. 



the load as closely as possible on the three phases which is best 
accomplished by entirely insulating adjacent trolley sections from 
one another and feeding three consecutive sections from each of 
the three phases. Such construction, of course, will not permit 
tying trolley sections together in case of emergency as in direct 
current distribution. 

In some instances three-phase generators are operated as 
single-phase machines at about two-thirds their rating. The 
simplicity of single-phase distribution and the ability to tie 




Fig. 37. 

adjacent sections of trolley together lend some advantages to this 
system for the shorter roads. 

The calculation of single-phase distribution systems is based 
upon the same laws as those previously outlined in detail, it 
being necessary only to substitute impedance for resistance in 
determining fall of potential in trolley feeder and track. It will 
be remembered that the apparent resistance or impedance of a 
conductor to the flow of alternating current is slightly greater than 
for direct current depending upon the size and material of the 
conductor as well as its position with respect to the return circuit. 
Tables of impedances for different sizes and spacings of wires 



DISTRIBUTION SYSTEM. IO3 

will be found in all electrical handbooks. The power loss calcu- 
lations for a given current are identical with those of the direct 
current system as the impedance does not enter these equations. 

Third Rail Distribution. — Practical difficulties in collecting 
large currents at high speeds by means of an overhead trolley have 
led to the installation of an insulated third rail or contact rail at 
the side and slightly above the running rails to which the positive 
feeders are connected and from which the current is collected by 
one or more iron contact shoes carried by each car. These shoes 
ordinarily bear on the head of the rail with their own weight but 
in some instances the third rail is inverted and protected with an 
insulating shield, in which case the shoe is pressed upward against 
the head of the rail by means of springs. Typical protected third 
rail construction is illustrated in Fig. 37, which shows very 
clearly the necessary break in the third rail at street crossings. 
This break is electrically bridged by means of a copper cable 
installed in conduit under the crossing. 

The calculations for third rail installations are identical with 
those for direct current trolley distribution, the resistances of the 
third rail, Table VIII, replacing those of the trolley wires. 

The relative advantages and disadvantages of the various 
systems whose method of distribution has been briefly described 
above will be compared in Part IV, Chapter I. 



CHAPTER III. 
Substation Location and Design. 

There is probably no question which the engineer of a pro- 
posed electric railway system has to decide that is more depend- 
ent upon good engineering judgment and common sense than 
that of the location of substations and power stations. Many 
theoretical rules and formulae have been devised for the purpose 
of calculating the most economical location of such a station and 
many of these must be given consideration and granted their 
proper weight in the final decision, but they are of little value 
when taken alone and often lead to serious errors when given too 
much prominence or when adopted with too little reference to 
local engineering and financial relations. 

With this foreword a few of the most important of these theories 
will be discussed, their relative importance being decided in 
each case by local and particularly by financial conditions. If 
the distinction between the design of alternating current sub- 
stations for single-phase lines and substations supplying 600 
volt direct current as subsequently outlined are kept in mind 
the following considerations may readily be applied to either type 
of station. 

Substation Location. — When a substation is being con- 
sidered whose function it is to supply power to a network of lines 
in a limited district of a large city system, one of the important 
considerations, as in the case of the power station, is to locate 
the station as nearly as possible at the center of gravity of the 
load. This center of gravity may be conveniently determined 
graphically as in problems in mechanics as follows. Locate the 
principal centers of distribution in the district, such as promi- 
nent street crossings and points from which several feeders 
radiate and determine the average load at these points as well 
as their distance apart. These may be graphically represented 
as in Fig. 38 with the loads considered as weights at the corners 

104 



SUBSTATION LOCATION AND DESIGN. 105 

of the diagram which is drawn to a convenient scale of distance. 
The center of gravity of the loads (A) and (B) would obviously 

AE 500 

be at (E) where =;^ = and AB or (AE+ BE) = 1.5 mi. while 

BE 200 

(D) and (C) might be combined into a single load of 1650 kw. 

at (F) where 

DF 1000 



CF 650 

The center of gravity of (E) and (F) with loads of 700 and 1650 
respectively located at (G) will therefore be the center of gravity 
of the system and from the standpoint alone of supplying the 
loads most economically this should be the location of the station. 



B-5C0 K.W. 



V 






^%^Ji0 




D- 650 K.W. 

Fig. 38. — Center of gravity of power demands. 

With the more common problem, however, of locating substa 
tions for interurban lines where the loads are usually located in a 
single straight line, the question to be decided is how far apart 
should the stations be placed in the single direction and there- 
fore how many and what capacity stations are necessary. The 
maximum distance between stations is limited by the voltage of 
the distribution system and in the case of the more common 600 
volt direct current distribution the distance between stations 
seldom exceeds 12 miles, each station feeding 6 miles in either 
direction. Whether this distance shall be diminished or slightly 
increased in each particular case depends largely upon the 
following considerations. 



Io6 ELECTRIC RAILWAY ENGINEERING. 

As the number of substations for a given road is increased 
and therefore the distance between them diminished the govern- 
ing factors will vary as outlined below. 

The total cost of buildings and real estate will usually in- 
crease in direct proportion to the increase in the number of sta- 
tions. This statement is, of course, subject to the qualification 
that such spacing of stations does not locate one or more of them 
in the centers of towns or cities, or in such other places as may 
increase their cost from the standpoint of high land values or 
expensive architectural effects. 

The cost of attendance will increase directly with the number 
of stations as the increased capacity of the fewer stations would 
seldom if ever require more attendants than the small station 
unless the station were located in a congested city district where 
the high cost of real estate necessitated double decking the station. 

The substation equipment will cost more with the increased 
number of stations but not proportionately more. Whereas 
much of the equipment will have to be duplicated with each 
station that is added and although the cost of small units is 
greater per kilowatt capacity than that of large machines, yet if all 
the stations considered are of fairly large capacity the relay capacity 
necessary for overloads of long duration and for emergency use 
will not be as great with an increased number of stations. This 
may be illustrated by assuming a total average demand upon all 
substations of 2000 kw. If two substations are decided upon, 
it would be good practice to install three 500 kw. units in each, 
or a total of 3000 kw., thus leaving one 500 kw. machine in each 
station as a relay. If, however, four stations seem advisable of 
500 kw. average demand each, it is probable that three 250 
kw. units would be used in each station requiring the same total 
of 3000 kw. While the switchboards, wiring, lightning pro- 
tection, etc., would therefore cost double the amount for the 
four stations, the machines and transformers would be increased 
in cost only by the increase per kilowatt of small as compared 
with large units, which increase between units of 250 and 500 
kw. is not great. Where the total demand on all stations is much 
less than that assumed in this case, however, the small station 
is at a disadvantage with respect to relay capacity and the in- 



SUBSTATION LOCATION AND DESIGN. I07 

creased cost of equipment may equal if not exceed the rate of 
increase in number of stations. 

The losses in substation machinery will increase slightly 
with increase in the number of stations because of the lower 
efficiency of smaller units and the increased no-load losses of the 
larger number of m.achines running light or idle for a portion of 
the time as is often the case in interurban stations. 

The cost of distribution copper and the losses in the distri- 
bution system will decrease with the increase in the number of 
stations, as the length and therefore the cost and resistance of 
feeders will decrease as the stations are moved nearer together. 

In order to reduce all of these quantities to common terms 
for comparison, an annual charge representing a certain per- 
determined percentage of the first costs involved must be com- 
bined with the annual cost of attendance, maintenance, and power 
losses. This percentage of the first cost which becomes an 
annual charge in all estimates of this nature is termed a "fixed 
charge" and involves interest on investment, taxes if any, insur- 
ance and depreciation on the equipment. This charge may be 
accurately estimated in each instance but is often assumed a total 
of II per cent, of the first cost whenever local conditions are such 
as not to eliminate any of the above mentioned items involved 
in, its makeup. If, therefore, a curve be plotted between ordinates 
representing the sum of fixed charges, annual cost of power losses, 
and maintenance and abscissas expressed in terms of number of 
substations, the total annual cost curve will result and because of 
the fact that some of the factors are increasing and some decreas- 
ing with an increase in the number of stations, a minimum 
point on the curve will be found which will denote the proper 
number of substations to install and therefore the distance 
between stations, considered solely from the standpoint of the 
factors involved in the curve. 

Such a method as that outlined above appears rather involved, 
requiring as it does at least a tentative station location, design of 
equipment, and feeder loss calculation for each group of stations 
considered. Since the capacity alone and not the detailed plan of 
the station changes with increased number of stations, and as the 
feeder losses in an interurban system will vary approximately 



Io8 ELECTRIC RAILWAY ENGINEERING. 

in proportion to the length of the feeders, the number of calcula- 
tions necessary for such a curve is not great and, as the cost varia- 
tions when thus graphically plotted are easily studied and com- 
pared, the solution is well worthy of serious consideration. 
Chapter II on the "Distribution System" will aid materially in 
the construction of these curves. 

It will be noted that nothing was said regarding the variation 
of transmission line costs and losses in the above discussion. 
While these factors may occasionally enter the problem in the 
case of city stations with underground high tension lines, yet in 
the case of interurban installations the transmission line usually 
parallels the road for nearly the entire distance, often looping 
through each of the substations en route. With such construction, 
it will be seen, the transmission line first cost and annual losses 
will not vary appreciably with substation location, especially for 
the reason that in the case of long lines with relatively small 
power requirements the transmission line wire is much larger 
than that required for any electrical considerations because of the 
mechanical strength needed. Even in high tension underground 
systems the substations are usually tied together by such a net- 
work of primary feeders for the sake of reliability of service 
that the first cost and annual losses in the primary system may 
be considered practically independent of the number of stations 
providing the total output does not change. 

Another important factor which should not be overlooked, 
especially when express and freight service is contemplated, is 
the question of combining the substation, waiting station, and 
freight or express depot into one building with a material saving 
in the item of substation attendance, since the substation operator 
can often attend to the other duties of the passenger station as well. 

If the station be not operated throughout the twenty-four hours 
the question of living accommodations for station attendants must 
be given some attention as the theoretical determination might 
locate the substations in localities where no attendants would be 
willing to live even though the railway company provided living 
apartments in the substation building as is often the case. With 
some of the shorter systems it is possible to connect the various 
sections of trolley and feeders through the substation switchboard 



SUBSTATION LOCATION AND DESIGN. lOp 

to the 600 volt direct current supply of the power station and 
thereby enable the first car in the morning to run over the line 
before the substations are started. With such an arrangement 
the operators may live in the nearest town to the substation. 

Substation Design. — Assuming the most common type of sub- 
station whose function it is to transform energy supplied by a high 
tension alternating current transmission line into direct current 
at approximately 600 volts, the principal factors entering into its 
design will be briefly discussed. 

With a knowledge of the load demand curve and the efficiency 
of the distribution system and with the number and location of 
substations determined, the average and maximum loads on the 
substation may be found as outlined in Chapter I. To decide 
upon the proper capacity of units to be installed, however, is 
largely a matter of good judgment. Since it is now standard 
practice to rate electrical machinery for a possible 25 per cent, 
overload for two hours without overheating, the duration of the 
peak load must be studied as well as its magnitude. It must also 
be known whether or not there is a possibility of greater loads at 
any time during the year and also what the growth in power 
demand is likely to be within the next few years. With these 
facts in mind it is well to provide for the average power by the 
installation of two or more units, usually leaving one unit as a 
relay in case of emergency. This relay unit should ordinarily be 
as large as the other units in the station in order that it may take 
the place of another machine in case of break down. Units of 
less than 200 kw. are seldom installed and if the average load 
is less than this value, the 200 kw. machines are usually run 
at light load rather than install smaller units. This procedure 
involves relatively large idle relay capacity as well but the smallest 
units are usually less reliable and offer little reserve capacity or 
inertia in case of sudden overloads. 

In the problem taken for illustration in Chapter I the average 
demand is 69.3 kw., while the maximum demand is 655 kw. 
The low average value is due to the fact that during several rather 
long periods there is no car on the section and the unit is there- 
fore running light. Further study of the curve will show that a 
load of 130 kw. is maintained for an hour at a time while peaks 



no ELECTRIC RAILWAY ENGINEERING. 

of 260 kw. exist for fifteen minutes. A 200 kw. machine would 
supply the average load and these latter peak loads but would not 
be of sufficient capacity for the peaks of 655 kw. caused by the 
simultaneous starting of two cars. A 300 kw. unit would there- 
fore be necessary for this station as it could withstand the momen- 
tary overload of 100 per cent. This case is a good example of the 
necessity of taking the overloads and their duration into account 
in such determinations. 

Synchronous Converter vs. Motor Generator. — Having 
determined upon the proper capacity for the unit a decision 
should be made between the synchronous converter and the motor 
generator. The former machine consists of a synchronous alter- 
nating current motor and direct current generator combined into 
a single unit with but one frame, armature, and field. It is really 
a direct current generator with the armature winding tapped to 
slip rings at symmetrical points, which rings are supplied with 
alternating current as in the case of the synchronous motor. The 
motor generator, as its name implies, is an alternating current 
motor direct connected to a direct current generator. The motor 
may be either of the synchronous or induction type. 

The advantages of each type of unit for railway substation 
service are briefly set forth in the following paragraphs : 

Advantages of Motor Generator. — The ratio between a. c. 
and d. c. voltage is not fixed. For transmission voltages not 
exceeding 13,000 this set may therefore be operated without step- 
down transformers if the motor be wound for transmission line 
voltage. 

The d. c. voltage may be readily controlled by means of the 
generator field rheostat without affecting the a. c. voltage or power 
factor. 

The d. c. generator may be automatically compounded or 
ovei -compounded without auxiliary apparatus. The converter 
requires an external reactance in addition to the series field. 

The motor generator is not as sensitive to commutation 
troubles, especially upon sudden overloads, as the converter. 

''Hunting," or the periodic variation in speed on either side 
of an average value, with the usual accompaniments of poor 
commutation and "arcing over" are less marked in the syn- 



SUBSTATION LOCATION AND DESIGN. Ill 

chronous motor generator set because of its greater inertia, while 
they are entirely absent in the induction motor set. 

The power factor of the synchronous motor generator set 
is controlled quite as easily as with the converter. The induction 
motor set, of course, has the disadvantage of low uncontrollable 
power factor. 

Advantages of Synchronous Converter. — This machine has 
a higher efficiency. 

Its rating for a given size of frame is much higher. 

The floor area taken up is considerably less. 

Its cost is less for a given capacity although, in cases where 
the adoption of the motor generator enables the transformers to 
be eliminated, the first cost of the converter with transformers is 
about the same as that of the motor generator alone. 

Methods of Starting. — Upon comparison of methods of start- 
ing there is found to be no choice between the two types of 
machines since both may be started from either the d. c. or a. c. 
side and with the latter method both machines may be started 
by either the variable voltage method of the General Electric 
Company or the auxiliary induction motor method of the West- 
inghouse Company If the direct current method of starting is 
adopted a starting rheostat must be provided which in turn will 
be controlled by a multi-point switch usually mounted on the 
switchboard. This switch starts the converter from the 600 volt 
feeder system as an ordinary d. c. motor, gradually cutting out 
resistance until the motor comes up to speed, when the man 
d. c. switch may be closed. The speed may then be varied by 
changing the field excitation until the a. c. side is synchronized, 
by means of the synchroscope or synchronizing lamps, as in 
the case of the synchronous motor or alternator. 

With the variable voltage method of starting low voltage taps 
are taken from the bank of transformers to a double throw 
switch usually located on a separate panel near the converter. 
When the switch is thrown down a low voltage, usually about 
one-third rated voltage, is impressed on the armature of the 
converter and the machine starts as an induction motor. As the 
converter approaches full speed the armature is supplied with 
full voltage by throwing the starting switch into the "up" position. 



112 ELECTRIC RAILWAY ENGINEERING. 

This method requires a rather large starting current at low power 
factor but has the advantage of eliminating the necessity of syn- 
chronizing. In both the above methods it is necessary to open 
the shunt field winding of the converter in several places in order 
that the excessive voltage otherwise induced in the many turns 
of the field by the large circulating currents in the armature may 
not puncture the field winding. 

If the auxiliary induction motor method be used a small 
induction motor, sufficiently large to start the converter with 
no load and bring it to slightly above synchronous speed, is 
mounted on the end of the converter shaft. This motor is usually 
operated by means of a three pole starting switch on the switch- 
board which is supplied with power from auxiliary transformer 
connections. As the converter reaches its proper speed it is 
synchronized with the transmission line as in the first case. The 
starting motor is then cut out of circuit. 

As each type of unit has many advantages and as both are in 
general use in railway substations it will be left to the engineer 
of each particular system to weigh the advantages and dis- 
advantages with reference to the local conditions under which 
they are to operate and to make the decision. It may be safely 
stated that the converter was at first installed almost universally 
in railway substations, but during the last few years the motor 
generator set has proved a formidable competitor and has been 
installed in many instances largely because of the commutation 
and hunting troubles which have been connected with the opera- 
tion of the converter in practice. 

Transformers. — If synchronous converters are installed to 
maintain a constant direct current potential, the secondary alter- 
nating current voltage which must be supplied to them is at once 
determined, since with the single armature of the converter there 
is a definite ratio between a. c. and d. c. voltages. This usually 
requires the installation of step-down transformers in order to 
lower the transmission line voltage to that value required by the 
converters. Even if motor generators are installed the trans- 
mission line voltage for interurban roads is usually so high that 
transformers are necessary in the substation. 

In Fig. 39 will be found an efficiency curve for a 750 kw. 



SUBSTATION LOCATION AND DESIGN. 



113 



three-phase synchronous converter from which it will be noted 
that although the efficiency falls off with light loads as with all 
other electrical machines, it may be considered constant for all 
loads above 50 per cent of its rating. The rated capacity of 
the converter divided by this efficiency constant will give the 
necessary transformer output. In this country almost universal 
preference has been shown for single-phase transformers com- 
bined into banks, usually of three each, in place of three-phase 



100 

90 

1 80 

|ro 

^60 















































































EFFICIENCY OF A 750 K.W. ROTARY CONVERTER 




















































































!_,-»-" 




















































y 


^ 
































/ 


/ 


































/ 




































/ 








































































' 

















































































































































30 



40 



60 80 100 

Percent Load 



120 UO 160 



Fig. 39. 



transformers. This is largely because of the increased flexibility 

of the system with smaller units and the avoidance of crippling 

the transformers of all phases in case of damage to a single unit. 

The rating of each transformer will therefore be determined as 

follows in the more common three-phase installation. 

Converter kw. 

Transformer kw. = — (80) 

3 X converter any. 

A bank of three transformers, each of the above rating, should be 
installed for each converter or motor generator usually with 
switches in both high and low tension connections. The trans- 
former connections may be either the well known "delta" or 
"star" on both primary and secondary, or either set of windings 
may be connected "delta" with the other "star" remembering 
8 



114 



ELECTRIC RAILWAY ENGINEERING. 



that with fixed transmission line and converter voltages the 

rated voltage of the transformers will be less than line voltage 

I 
in the ratio of —r^ if the "star" connection be adopted. The 

V3 
"delta" connection has the advantage of continuing three-phase 

operation with two transformers "V" connected in case of damage 

to one unit without change of connections. Its further advantage 

of changing to "star" connection at some future time in case it 

seems desirable to raise the transmission line voltage should not 

be neglected in making a decision. 

Table IX will be found convenient in selecting transformer 

voltages for converters of various types. This table is based 

upon 600 volts at the direct current side of the machine and while 

it represents average practice it must be remembered that the 

voltage ratio is dependent upon the design of machine and may 

therefore vary slightly with machines of different manufacture. 



TABLE IX. 

Voltage Ratios in Synchronous Converters. 






Actual ratio. 


Theoretical 
ratio. 




Zero load. 


Full load Full load 
(straight). (inverted). 

i 


Single phase 

Three phase 


429 
366 


435 
372 


423 
360 


424 
367 



In many substations six-phase synchronous converters will be 
found operating upon three-phase transmission systems. This 
procedure is adopted because of the higher efficiency and greater 
output of the six-phase machine for the same size of frame. The 
connections and switching apparatus of the six-phase converter 
are necessarily more complicated than with the three-phase 
machine. From Table X which illustrates the increased capacity 
of converters of different phases for the same size of frame it will 
be noted that a six-phase converter has nearly double the capacity 



SUBSTATION LOCATION AND DESIGN. 



115 



of the same machine operated as a direct current generator and 
nearly one and one-half times that of a three-phase converter. 
If a sufificently large commutator and brush rigging be provided 



Ap 

VvwvwvW 



Bp 

Vxaaaaaaaa/ 



AAAA, 

A 



Cp 

VVVVVWA/W 




ad of eh 

Fig. 40. — Six-phase "delta" connections from three-phase primaries. 
(Double secondary required.) 

on a three-phase machine rated at 500 amperes, it may be used 
as a six-phase machine, if properly connected, for an output of 
725 amperes with the same temperature rise. 



NAAAAAAAAA/ 



AAAA 




B: 



vwwvwvv 



AAAA 



c. 



XAAAAAAAAA/' 




AAAA A 

10 




Fig. 41. — Six-phase "star" connections from three-phase primaries. 
(Double secondary required.) 

TABLE X.i 
Comparative Ratings of Converters. 



D. c. 

generator. 


Single-phase 
converter. 


Three-phase Two-phase 
converter. j converter. 


Six-phase 
converter. 


1 .00 


0.85 


1.32 1.62 

i 


1 .92 



^ Elements of Electrical Engineering, Vol. II, Franklin and Esty. 



ii6 



ELECTRIC RAILWAY ENGINEERING. 



The above discussion has a direct bearing upon the question 
of transformer connections, for if a six-phase converter be in- 
stalled one of the methods of connection illustrated in Figs. 40, 
41, and 42 must be adopted if the three-phase supply is to be 
retained. 

Transformers may be further classified with regard to their 
method of cooling as follows : 

1. Oil cooled. 

2. Air cooled. 

3. Water cooled. 



vww vww wwv 

AA^V\ /VWV\ /WVVX 




Fig. 42. — Six-phase diametrical connections from three-phase primaries. 

(Single secondary only.) 

Transformers of the ''oil cooled" class depend for their cooling 
upon the natural circulation of a comparatively large body of 
oil within the transformer case, all the heat being radiated from 
the surface of the corrugated iron cases. This construction is 
suitable for transformers of all potentials and for capacities up 
to 500 kw. 

Air cooled transformers are cooled by means of an air blast 
provided by a motor driven blower and forced through the air 
ducts of the transformer core. This method of cooling requires 



SUBSTATION LOCATION AND DESIGN. II7 

the construction of air ducts in the floor, usually of concrete, and 
involves the additional cost of blower outfits. It is suitable for 
all capacities but is limited to potentials of 33,000 volts or less. 

Transformers of the third class contain a series of pipe coils 
within the case, the insulating oil circulating around the coils 
while the latter are cooled by means of circulating water within. 
This type of transformer is used for all the largest installations 
and is not limited as to capacity or voltage. 

Compounding Reactances. — One of the disadvantages of 
the synchronous converter is the difficulty of compounding the 
machine for constant or increasing d. c. voltage with increase 
of load. This difficulty arises from the fact that when the field 
strength of the converter is varied its direct current voltage is 
not appreciably changed. The converter acts as a synchronous 
motor in this respect, the increase of field strength causing the 
motor to draw a leading current from the line. It is this latter 
feature that makes it possible to compound the converter if an 
external reactance be connected in series with each of the phases 
between the transformers and the converter. If the machine be 
designed to give rated voltage at a light load with the reactance in 
circuit, it follows that the leading current produced by a series 
field as the load increases will neutralize the inductive voltage 
of the reactance coil and thereby impress an equal or even higher 
voltage on the converter at full load. As there is a fixed ratio 
between the a. c. and d. c. voltages, the latter is compounded at 
the same time. The combination of series field and external 
reactance is therefore necessary for compounding a converter, 
whereas the former only is required for the d. c. generator of the 
motor generator set. 

Switchboard. — The typical substation switchboard consists of 
the following classes of panels : 

1. High tension line. 

2. High tension transformer. 

3. A. c. converter or motor generator. 

4. D. c. converter or motor generator. 

5. Totalizing. 

6. D. c. feeder. 

The number of panels in each class is dependent upon the size of 



Il8 ELECTRIC RAILWAY ENGINEERING. 

station and the number of converters it contains but all panels 
of each class are usually grouped by themselves. 

The two classes of high tension panels are usually of the remote 
control type. This is universally the case above 13,000 volts. 
With this construction the high tension switches are mounted in 
fire-proof compartments of concrete, tile, or brick and may there- 
fore be located at some distance from the control board. No high 
tension lines are connected with the control board, the switches 
being operated by means of auxiliary 125 volt d. c. circuits and 
the meters connected with the secondary windings of current and 
potential transformers whose primary windings are in the high 
tension circuits. Red and green illuminated bulls-eyes on the 
switchboard panels indicate whether the main switches are closed 
or open respectively. 

The high tension line switches control the connections between 
high tension lines and the station bus bars, while each bank of 
transformers is connected to the high tension buses by means of 
the switches controlled by the panels of the second group. These 
latter switches and often both groups of switches are provided 
with inverse time limit relays which act as circuit breakers in case 
of overload, with the further provision that they may be adjusted 
to operate only after the overload has continued for a prearranged 
interval. The "inverse" type of relay is in addition so designed 
that the greater the overload, the shorter will be the time in 
which it will open. With the transformer relays set for a very 
short interval, the high tension line switches arranged so as to 
open a fraction of a second later if the overload still continues 
and with the relays in the out-going high tension feeders at the 
power house adjusted for an interval of one or two seconds, it 
will be seen that only those switches connecting apparatus or 
lines upon which there is trouble will be opened and the inter- 
ference with other service reduced to a minimum. 

The meters to be installed on the first two groups of panels 
often vary widely with the personal preference of the engineer 
in charge, an average equipment probably consisting of an am- 
meter in each phase, a power factor meter and a voltmeter on a 
swinging bracket at the end of the board. 

The panels of group three contain all equipment necessary for 



SUBSTATION LOCATION AND DESIGN. 



119 



the control of the a. c. side of the converter or motor generator 
as the case may be and usually include a low voltage secondary 
a. c. switch for connecting converter to transformers, motor field 
rheostat in case of a synchronous motor generator set, starting 
switch if starting motor be used, together with synchronizing and 
voltmeter plugs. The instruments usually consist of three am- 
meters and a power factor meter. 

The direct current panels perform the office of connecting the 
direct current or output side of the converter or motor generator to 




Fig. 43. 



the direct current bus bars. For this function three single pole 
switches are usually employed, one positive, one negative, and an 
equalizer switch. The negative and equalizer switches are often 
located on a pedestal or on the frame of the converter thereby 
simplifying the switchboard connections. The field rheostat con- 
trol of the converter or of the generator of the motor generator 
set is located on this panel together with a circuit breaker, a d. c. 
potential receptacle, and a starting switch in case it is planned to 
start the machine from the d. c. side. The meters are usually 
confined to a main ammeter and indicating wattmeter with a d. c. 
voltmeter on a swinging bracket. In large installations a field 
ammeter is often included on this panel. 



120 



ELECTRIC RAILWAY ENGINEERING. 



The totalizing panel contains instruments only and these are 
so connected as to measure the total output of the station between 
the d. c. converter panels and the outgoing feeders. An ammeter 
or indicating wattmeter and an integrating wattmeter are 
usually installed. This panel is often entirely omitted and the 
latter instrument mounted on the sub-base of one of the other 
panels. 

The out-going feeder panels may be designed to control one 
or t\vo feeders each. Single pole (positive) switches and circuit 
breakers in series with ammeters make up the usual equipment 
for each feeder. 




Fig. 44. 



The entire board is usually of the standard size 90 in. 
in height including a 28-in. sub-base with panels varying in 
width from 16 to ^6 in. Blue Vermont marble forms the 
principal material of construction although low voltage boards are 
often built of slate. The board should be spaced at least 4 ft. 
from the wall and the wiring at the back should be generously 
lighted. Where gallery boards of the remote control type are 
installed from which the operator may view all the machines 



SUBSTATION LOCATION AND DESIGN. 



121 



under his control, the "desk type" of board has been quite 
frequently specified. In Figs. 43 and 44 will be found views of 
typical railway substation switchboards. 

Storage Battery Auxiliary. — While the storage battery is 
looked upon by many engineers and managers as an evil to be 
avoided, it certainly has its important place in the substation 
equipment of many roads. Its possible function is three-fold, 
although it is often installed for the purpose of meeting but one of 
the following requirements : 

1. To aid in maintaining constant potential. 

2. To supply all peak loads above a certain predetermined 
average. 

3. To assume the entire load of the substation for a short 
period of time. 




Fig. 45- 



When the second and third functions listed above are assumed 
by the battery, its capacity must be rapidly increased, yet in 
many instances batteries of sufficient capacity to fill these three 
requisites are maintained in practically all substations of the 
road. 

As the maintenance and depreciation of a battery is relatively 
high, the local problem must be carefully studied before a decision 
can be reached. Such a study should balance the fixed charges of 
the battery and accompanying control equipment combined with 



122 



ELECTRIC RAILWAY ENGINEERING. 



its maintenance, against the fixed charges of the relay equipment 
and the extra line copper that would otherwise have to be installed, 
plus the rather intangible factors of irregular schedule due to 
variable voltage and total interruption to service. 

Arrangement of Apparatus.— There is little variation in the 
arrangement of apparatus in a railway substation except in the 
extreme cases where it is necessary to locate the equipment on 




L Grade 



S K4^5->| 



K-5— 2-^ l«-5-2-^l 

Fig. 46. 



N-5-l-'-?>i 



two floors. The high tension apparatus is usually confined to a 
separate room and is often located in fire-proof vaults. The 
converters, reactances, and switchboard are usually located very 
close together in a single room with the wiring either in conduit 
embedded in the floor or of the open type supported from insulator 
racks on the basement ceiling. The principal features which tend 
materially to alter the design of a substation are the overhead or 
underground entrances of high tension and d. c. feeder cables. 



SUBSTATION LOCATION AND DESIGN. 



123 



Typical stations involving each type of construction are illustrated 
in Figs. 45 and 46. 

Wiring. — The wiring of the station is usually figured from the 
standpoint of carrying capacity only, as the potential drop for 
the short distances involved is generally negligible. The resist- 
ances of the d. c. cables between converter and switchboard 
should, however, be carefully balanced in order to divide the 
load properly between two or more machines operating in parallel. 




Fig. 47. 



The low tension wiring and the high tension cables up to 13,000 
volts are usually insulated with rubber, paper, or varnished 
cambric and protected either with braid or a lead sheath. Such 
construction is well illustrated in Fig. 47, while a simplified wiring 
diagram for a typical substation will be found in Fig. 48. Wiring 
above 13,000 volts, and often that at lower voltage is carried on 
line type insulators with no further insulation, these lines often 
being run in individual concrete or brick compartments with con- 



124 



ELECTRIC RAILWAY ENGINEERING. 




:iC°-l {K]4wvVv| H 



^( °— ^V-/VWVW. 



SUBSTATION LOCATION AND DESIGN. 



125 



venient chambers provided for sectionalizing or disconnecting 
switches and instrument transformers. 

Lightning Protection. — The incoming high tension lines and 
the outgoing railway feeders are each provided, just within the 
wall of the station, with a helix of wire of the same size as the line 
wire which acts as a "choke coil" to divert high frequency surges 
to the lightning arresters connected between the coils and the 




Fig. 49. 

outside lines. These arresters which will be found described at 
length in manufacturers' bulletins usually comprise a series of 
spark gaps between the lines and ground which will permit a 
discharge to pass when an excessive voltage occurs and yet quench 
the arc which would otherwise follow over the gaps when supplied 
with normal line potential. The recent type of electrolytic 
arrester. Fig. 49, however, interposes a series of liquid films of 
high resistance in place of the spark gaps and is therefore self 



126 



ELECTRIC RAILWAY ENGINEERING. 



healing. Two objectionable features of this arrester, however, 
are its tendency to freeze in cold weather and the necessity of 
''charging" it from time to time to maintain the films of electrolyte 
in working order. 

Portable Substations. — On many roads trafi&c demands 
become excessive upon certain days or weeks of the year on differ- 





FiG. 50 



ent sections of the line. A means of meeting this local and 
temporary demand for power has been found in the ''portable 
substation," Fig. 50, which usually consists of a box car with a 
converter, transformers, switchboard, etc., complete and ready 
for connection to the high tension lines at any point on the 
system and capable of operating in parallel with the permanent 
station on any desired trolley section. Such a portable station has 



SUBSTATION LOCATION AND DESIGN. 



127 



proved a means of providing good service under extreme con- 
ditions not only, but has protected the regular equipment from 
damage due to serious overload as well. 

High Voltage Direct Current Substations. — Within the last 
few years the 1200 volt direct current railway system has been 
developed and some dozen interurban roads are now operating 
on this voltage. This increase of voltage decreases the first 
cost of installation as it reduces the number of substations neces- 
sary as well as the amount of distribution copper required. A 
more detailed comparison of its cost and advantages will be 
found in a later chapter. 




Fig. 51. 

The substation design for such a system is not materially 
different from that outlined above except in the case of the con- 
verting equipment. Two standard 600 volt machines, connected 
in series, are usually installed for this service, the negative terminal 
of one unit being connected to the rail while the positive lead from 
the second machine is carried to the switchboard bus bars and 
thence through 1200 volt feeder panels to the feeders and trolley. 
Fig. 51 shows the synchronous motor generator set used for such 
service in the substation of the Pittsburg, Harmony, Butler, and 
New Castle Railway while the wiring diagram for this station 
will be found in Fig. 52. It should be noted that in this in- 
stallation no transformers are used although the synchronous 
motor of the motor generator set operates at 13,200 volts. 



128 



ELECTRIC RAILWAY ENGINEERING. 



Single-phase Alternating Current Substations. — In systems 
where single-phase alternating current is supplied to the car in 
place of direct current there is, of course, no demand for the 
conversion of alternating current to direct current in the sub- 
station. On long lines, however, substations are still necessary 



Swing. 

ing 
Bracket 


2C.S.F. 

Panels 
1200 V. 




333 A. 



2C.S.G. Panels 1200 V 
400 Kw. 



C.D.G. 
2 ^ T Y Panels 125 V.D.C. 6 Kw- 13200 V.A.C. 
400 Kw. 

Incoming Lines 




Synchronous 
Motor 

*— — Bus (Grrounded) 
i!biqualizer 

Fig. 52. 

to reduce the potential of the transmission line to that suitable 
for the trolley, the latter voltage usually being 6,600 or 13,000 
volts. Such substations involving only transformers, lightning 
protection, and switches, require no attendants and are therefore 
very small and simple in design as compared with the stations 



SUBSTATION LOCATION AND DESIGN. 



129 



previously considered. Automatic oil switches are usually 
installed in both primary and secondary circuits of the step-down 
transformers although in this case the time element of the auto- 
matic relay is adjusted for a greater time interval than those at 
the power station in order that the latter switches will open first 
in case of trouble. This method, which is just the reverse of that 
in converter substations, is adopted to avoid frequent trips to the 




Fig. 53. 



substation to close switches. The accompanying Fig. 53 illus- 
trates one of the stations of this type on the Chicago, Lake Shore, 
and South Bend Railway which is probably the longest interurban 
system operating single-phase in this country. 

Substation Cost. — The following working estimate prepared 
to cover the total cost of fou^* substations of the 600 volt direct 
current type for a 63-mile interurban line in the South may be 
useful in determining the relative' cost of substation equipment. 
As each station contains one synchronous converter of 300 kw., 
the costs may be figured on a basis of 300 kw. per station. 
9 



130 ELECTRIC RAILWAY ENGINEERING. 

4 Substation buildings, @$4.oo kw $4,800 

4 Converter foundations, 150 yd. @ $8.00 1,200 

4 Transformer banks, 1320 kw. @ $10.00 13,200 

4 Converters, 1200 kw. @ $16.00 19,200 

Freight and erection, 3,000 

4 Switchboards, 4 panels each . 8,800 

Freight and erection 1,600 

Wiring, @ $1.50 per kw 1,800 

High tension switch cells 1,000 

Lightning protection 2,400 

Total. @ $47.50 kw $57,000 

Whereas the discussion in this chapter covers the principal 
features of substation location and design, many special features 
with regard to operating costs and the function which the sub- 
station has to play in the various types of distribution systems 
will be considered briefly in succeeding chapters. 



CHAPTER IV. 
Transmission System. 

The necessity for greatly detailed calculations in designing 
high tension transmission lines for railway systems is often ex- 
aggerated. The fact that the careful predetermination of all 
characteristics of such a transmission line is unnecessary, when 
compared with the careful study required in connection with a 
line for the transmission of power for lighting or even for the very 
high voltage long distance transmission of energy in large quan- 
tities from hydro-electric plants, will be made clear by the following 
outline of conditions generally pertaining to the railway system. 

In the first place the close regulation of voltage is both un- 
necessary and impossible. The sudden variations of power de- 
manded by cars, especially upon an interurban system, must 
inevitably mean variable voltage and with such voltage variation 
on the distribution system there is little need of the closest possible 
regulation on the transmission line. 

Nor is the service impaired by such voltage variation as would 
be suicidal to the lighting substation. The motorman or pass- 
engers upon an interurban car will hardly notice a ten per cent. 
voltage variation, while sudden variations of 2 or 3 per cent, are 
to be avoided if possible in connection with incandescent lighting, 
particularly as the intensity of light varies throughout a greater 
range than the voltage. The lighting of interurban cars is of 
course greatly impaired by poor voltage regulation and this is 
one of the features that is receiving a great deal of just criticism 
from the traveling public. Its remedy, however, lies in making 
the lighting independent of trolley voltage and not by attempting 
to regulate the latter more closely. 

The regulation of transmission lines is greatly affected by low 
power factor. The addition of induction motors or arc lighting 
systems which operate at low power factors to long distance 
transmission lines involves very careful design and costly reg- 
ulating apparatus if lighting loads are to be successfully supplied 
by the same line. In many such instances synchronous motors 
are installed, often without direct financial return to the company, 

131 



132 ELECTRIC RAILWAY ENGINEERING. 

in order that the power factor may be properly controlled. Such 
control is present in the railway substation in either the synchro- 
nous motor generator set or converter and with little practice the 
substation attendant can maintain very nearly unity power factor 
on the transmission line and thereby aid its regulation to a great 
extent. 

Many of the limiting factors in high tension line design such 
as the pin type of insulator, corona losses, troubles introduced by 
wide spacing and long spans, etc., are introduced only when the 
voltage becomes higher and the amounts of power become much 
greater than those involved in the major part of the interurban 
transmission. In fact a census of transmission lines for railway 
purposes only would probably reveal the fact that an extremely 
small percentage of these lines are above 33,000 volts. At this 
voltage two parallel three-phase circuits on pin type insulators 
and wooden poles carrying in addition the distribution feeders 
and trolley brackets represent common practice. Such a line in 
the Middle West has for years been satisfactorily operating an 
interurban system no miles in length at 33,000 volts. In such 
design simple electrical and mechanical considerations are alone 
involved. 

For the above reasons, therefore, and because of the very able 
treatises in complete volumes devoted to the details of this subject, 
an exhaustive study of transmission line design will not be at- 
tempted in these pages. 

The three-phase system of alternating current transmission 
has been standardized almost exclusively for railway work. This 
is principally because polyphase apparatus is necessary for sub- 
station units in large sizes and in addition because the three-phase 
system requires but three-fourths the copper of the single-phase 
installation. Other polyphase systems, although more economical 
in copper in some instances, have not found favor largely because 
of the complication introduced by the greater number of wires. 
While six-phase substation apparatus was shown in the preceding 
chapter to be highly desirable, the possibility of its operation from 
a three-phase line has introduced no serious consideration of 
six-phase transmission. For these reasons, therefore, three-phase 
transmission only will be herein considered. 



TRANSMISSION SYSTEM. 1 33 

Mechanical Strength. — Owing to the fact that calculations 
of the proper size of wire for transmission lines based on Kelvin's 
law, voltage regulation, and carrying capacity, in most cases 
result in a wire too small to withstand the mechanical stresses 
incurred by ordinary line construction and weather conditions, 
the mechanical strength of the line may well be considered first 
and the size of wire checked in accordance with the electrical 
considerations later. No wires smaller than No. 4 B. & S. 
hard drawn copper or its equivalent in tensile strength should 
be used for mechanical reasons. If aluminum be used it should 
be remembered that for the same size aluminum weighs about 
30 per cent, and has a resistance of i . 67 times that of hard drawn 
copper. Aluminum costs considerably less than copper for the 
same conductivity and melts at a much low^er temperature. It 
also has a greater coefficient of expansion causing greater vari- 
ation in sag with change of temperature. It is difficult to solder, 
is quickly attacked by gases in the atmosphere and has a tensile 
strength of approximately one-third that of copper. In spite 
of its many disadvantages aluminum is used to a considerable 
extent for line construction largely because of its low cost and 
light weight. Joints are made mechanically by overlapping the 
ends in an oval sleeve and twisting the sleeve and wire ends to- 
gether without solder. On account of its large diameter for a 
given conductivity the total wind pressure on a line is greater and 
because of its low melting point it is more likely to melt apart 
than is copper in the event of an arc forming between wires. 

The question whether one or two parallel three-phase lines 
shall be installed, one for the purpose of acting as a relay for 
the other in case of break-down is an open one and is generally 
decided by the personal preference of the engineer in charge. If 
a single line only be installed it is usually mechanically stronger 
and therefore better able to withstand abnormal strains. In 
this case the wires are spaced at the vertices of an equilateral tri- 
angle with one wire on the pole top and the two lower wires on a 
single cross arm. If two circuits are employed two arms are used 
and one circuit is installed on either side of the pole. Such con- 
struction permits repairs to be made on one of the lines with the 
other in operation when the voltage does not exceed 33,000 volts. 



134 ELECTRIC RAILWAY ENGINEERING. 

No particular specifications need be made for the poles, which 
are also used for the trolley span wires, feeders, and probably 
signal and telephone circuits as well, except that they must be 
sufficiently high to give sufficient clearance to the high tension 
wires during the period of maximum sag and that they be at least 
7 in. in diameter at the top. The forces acting on the poles 
due to the presence of the high tension line are. 

Vertical downward force due to weight of conductors with 

possible ice sheath and vertical component of wire tension. 

Bending moment due to angle in line or with one or more 

wires broken. 

Bending moment due to wind pressure on pole and ice 

sheathed wires. 
Although these forces may be readily calculated by means of the 
fundamental laws of mechanics, it is safe to assume that there is 
a sufficient factor of safety with a properly constructed pole line 
sufficiently heavy for the trolley and feeder installation for the 
reason that the latter acts as a longitudinal anchor guy in case 
of a broken high tension wire and owing to the further fact that 
the possible strains on the high tension line are generally small 
as compared with those incurred by the feeder and trolley 
construction. 

Electrical Considerations. — Considering the large number 
of railway high tension lines using No. 4 B. & S. wire, and 
remembering that this should be a minimum for mechanical 
reasons, it will probably save time in calculation to assume this 
size at the start. A convenient spacing for wires not exceeding 
33,000 volts is 36 in. With these dimensions in mind it 
will be remembered that in determining the regulation of an 
alternating current line the impedance must be considered in 
place of the resistance which is used in direct current calculations. 
Impedance may be considered as the resultant of the resistance 
and the reactance of the line combined at right angles. In other 
words, 

Z = \/RHX' (81) 

where Z = Impedance of line in ohms. 
R = Resistance of line in ohms. 
X = Reactance of line in ohms. 



TRANSMISSION SYSTEM. 1 35 

The reactance (X) of a transmission line is partly due to in- 
ductance (L), which in turn is dependent upon the cutting by 
the wire of lines of force set up by the current in the wire, and the 
capacity (C) which is the effect due to the wires acting as the 
plates of condensers with the air as a dielectric medium between. 
Since the formulae for these quantities given below show that the 
capacity is decreased and the inductance increased as the wires 
are moved apart and also as the size of wire is decreased, these 
two functions of reactance will be seen to be opposed to one 
another, one neutralizing the other to some extent. Since the 
capacity effect is relatively small, especially on the average short 
line of the inter urban railway operating at moderate voltage, it 
will be neglected in the first determination of regulation and the 
error introduced by such a procedure pointed out later. 

As the theoretical proof of the formulae for line inductance and 
capacity is beyond the scope of this book and as their methods 
of derivation are included in most theoretical treatises on electri- 
cal engineering they are listed below without proof. 

0.0776 1 
C=-^'-^ (82) 

2 log. 10 J. 

L=. 000322 (2. 303 logio(y-) +0.25)1 (Ss) 

where L = Self inductance per wire in henries. 

d = Distance between wire centers in inches. 
r = Radius of wire in inches. 

C = Capacity between one wire and neutral point in micro- 
farads. 
1 = Length of circuit in miles. 
Considering only the resistance and inductive reactance of the 
line at present the latter may be found from the equation, 

X^=2 7:fL. (84) 

where Xl= Reactance due to inductance in ohms. 
f = Frequency in cycles per sec. 
L = Inductance from equation (Si,) in henries. 
Tables giving such of the inductive reactance values and re- 
sistances as will be needed in railway transmission line calcu- 
lations are given below. 



136 



ELECTRIC RAILWAY ENGINEERING. 



TABLE XI. 1 
Inductive Reactance of Single Wire in Ohms per Mile. 









Spacing inches 25 


cycles. 








Size wire. 




















24 


36 


48 


60 


72 


84 


96 


108 


120 


150 


350000 cm. 


•235 


•255 


.270 


.280 


.290 


.298 


•304 


.310 


•315 


•327 


300000 


.238 


.258 


•273 


.285 


.294 


.301 


.308 


•314 


.320 


•330 


250000 


.242 


.263 


.278 


.289 


.298 


•305 


■3^3 


•319 


•324 


•335 


4/0 B & S 


.248 


.268 


.283 


•294 


•303 


.310 


.318 


•325 


•329 


•340 


3/0 


• 254 


.274 


.289 


.300 


•309 


■3T^7 


•324 


•330 


•335 


•346 


2/0 


•259 


.280 


•294 


.306 


■315 


•323 


•329 


•335 


•341 


•352 





.265 


.286 


.300 


•3" 


.321 


•329 


■335 


•341 


•347 


•358 


I 


.271 


.292 


.306 


.318 


•327 


•334 


•341 


•347 


•352 


•364 


2 


.277 


.297 


.312 


•323 


•332 


•340 


•347 


■353 


•358 


•370 


3 


•283 


■303 


.318 


•329 


•338 


•345 


•352 


■359 


•364 


•375 


4 


.289 


•309 


•324 


•335 


•344 


•352 


•359 


■365 


•370 


.381 


6 


.300 


.321 


•335 


•347 


•356 


•363 


•370 


■376 


.381 


•393 



TABLE XII.i 
Resistance of Copper and Aluminum at 70^ Fahr. 



Ohms per mile. 



Size wire. 




500000 cm. 


.109 


.176 


450000 


.121 


.196 


400000 


■137 


.221 


350000 


.156 


.252 


300000 


.182 


• 294 


250000 


.219 


•353 


4/0 B&S 


.258 


.417 


3/0 


.326 


.526 


2/0 


.411 


.664 





.518 


•837 


I 


•653 


^•055 


2 


.824 


^•330 


3 


1.039 


1.678 


4 


1.309 


2. 116 


6 


2.082 


3 •309 



^Standard Handbook, Section 11, p. 40. 



TRANSMISSION SYSTEM. 137 

Since the power factor at the substation may be maintained 
at approximately loo per cent, by control of the field of the 
synchronous converter or motor generator, such a power factor 
may be safely assumed in line calculation. In fact it would not 
introduce a serious error to neglect impedance of the line entirely 
and solve the problem as if for a direct current system since even 
the effect of line reactance may be overcome by careful regulation 
of the substation apparatus as explained above. 

Voltage Determination. — The voltage and current per wire 
must now be determined. They are principally dependent upon 
the substation input and distance of transmission. 

In deciding upon the proper voltage for the transmission line 
as well as in selecting electrical equipment it is necessary to take 
into consideration the standards established by the manufacturers. 
Primary substation voltages have been standardized as follows: 
11,000, 19,100, 33,000, and 66,000 volts. The two lower potentials 
are most often used with "delta" connections while voltages of 
33,000 and 66,000 are obtained with "Star" connected trans- 
formers. It should be noted that the three lower voltages bear 
the ratio of \/^ to one another thus permitting the next higher 
standard voltage to be obtained by changing connections of trans- 
formers from ''delta" to "star." For a rough selection of the 
voltage to be first used for calculation, looo volts per mile of trans- 
mission are often used. As local conditions enter into the problem 
to a marked degree, and since it is almost impossible to express 
intelligently in equation form all the factors entering into the 
selection of the proper voltage from the standpoint of regulation, 
first cost, and economical operation, it seems advisable to select two 
of the nearest standard voltages by the above rule and compare 
the resulting calculated data of the two cases before finally 
determining upon the best operating voltage. 

Regulation. — The transmission line calculations are usually 
based upon the combined substation inputs supplied by a single 
line at full rated load although, if the number of substations be 
large, it may be found from a study of their load curves that their 
maximum loads do not occur simultaneously and that the total 
demand on the transmission line may be considerably below the 
summation of the substation ratings. The rated output of the 



138 



ELECTRIC RAILWAY ENGINEERING. 



substation transformers was found in Chapter III equation (80). 
The input to the station may be obtained from the above by 
dividing the output of all transformers by the transformer effi- 
ciency which may be safely assumed for large transformers at 
full load as 98 per cent. 

The current per wire on the transmission line is therefore 

Kw. X 1000 

V 3 hj cos 
where I^ = Current per wire in amperes. 
Kw = Substation input in kilowatts. 
E = Voltage between wires at substation, 
cos = Power factor of load at substation. 
For this calculation (cos 0) is taken as unity as explained above. 




Fig. 54. — ^Vector diagram for transmission line regulation unity power factor. 

The impedance of the transmission line may now be found 
from equation (81) if values of reactance and resistance from 
Tables XI and XII for No. 4 B & S wires spaced 36 in. apart 
be substituted. The voltage drop on the line is 

e = IwZ ' (86) 

These relations including the generator voltage (Eg) are shown 
in Fig. 54 from which the value of Eg may be derived. 

E, = V(E3+I„R)H(I„XJ^ (87) 

where (Eg) represents substation voltage between wire and 

E 

neutral or 



Vs 



Reg 



E. 



(88) 



If less than unity lagging power factor be assumed as in 
the case of an induction motor generator set for example, other 
conditions remaining the same, a larger current (I'^) would have 



TRANSMISSION SYSTEM. 



139 



resulted from equation (85) and the voltage diagram would appear 
as in Fig. 55, the resulting generator voltage being 

E'^ = ^y(E,cos4>+I\,Ry+(E^sm<l> + I'J^y (89) 
As before, the percentage regulation may be obtained from the 
equation 

Reg' = ^^^ (90) 

If the regulation from either equation (88) or (90) is unreason- 
ably high, a suitable value, say 10 per cent., may be substituted 
back into the equation and corresponding values of Eg or E'g found 




IjfX; 



EsCos0 
Fig. 55. — ^\^ector diagram for transmission line regulation lagging power factor. 

from which the correct value of (R) may be calculated by means of 
equation (87) or (89) and the proper size of wire obtained from the 
wire table. 

As a concrete illustration of these two approximate methods of 
obtaining regulation, assume the following conditions, 

Substation input = 1500 kilowatts. 

Power factor = 100 per cent. 

Length of line = 50 miles. 
Using No. 4 wire and a substation voltage of 33,000, there results, 

R =1.309 X 50 = 65.4 ohms. 

X^=o.3i X 50 =15.5 ohms. 

33000 
E_ per terminal = -—.-^= 19,100 volts 
V3 



Z = V(65.4)H(i5-5)' = 67ohms. 
1,500,000 



'^ 33, 000 \/3 



26. 2 amp. 



Eg = \/(i9, 100+26. 2x65. 4)'+(26. 2 X 15.5)^ = 20,820 (87) 



I40 ELECTRIC RAILWAY ENGINEERING. 

20,820— 19,100 

Reg = = 9 per cent. (88) 

19,100 

Now suppose the power factor to be lowered to 85 per cent, by 

low field excitation of synchronous apparatus or the operation of 

an induction motor generator set. 

1,500,000 
^-^3,oooV^xo.85^^°-9amp. (85) 

E'g=\/(i9>ioo X -85 + 30.9 X 65.4)^(19,100 X 0.527 + 

30.9x15.5)^ = 20900 (89) 

20,900—19,100 

Reg' = = 9-43 per cent. (90) 

19,100 

Both the regulation for 85 per cent, power factor and unity 
power factor are sufficiently small for railway service and the 
conditions of size of wire, voltage, spacing, etc., may be tentatively 
decided upon and checked further with regard to Kelvin's law, 
carrying capacity, etc., as explained under " Distribution System." 

Capacity Effect. — Since, however, the capacity has been 
entirely neglected in the above calculations, the error introduced 
by such omission should at least be pointed out. 

As previously explained, the line wires act as plates of a con- 
denser and thus draw a leading "charging" current from the 
power house just as an infinite number of small condensers would 
do if connected in parallel across the line wires throughout their 
entire length. As such a uniform distribution of capacity involves 
a constantly changing charging current, power factor, and voltage 
throughout the entire length of the line, which condition can be 
represented only by a rather involved mathematical equation, it 
has been shown by Steinmetz^ that this capacity effect may be rep- 
resented sufficiently accurately by locating one-sixth of the total 
capacity at either end and two-thirds in the middle of the line. 
In fact, little error is introduced if the entire capacity is con- 
sidered in parallel with the line at either the generator or 
receiver end. Adopting the latter assumption the equations 
below show the method of derivation of the values in Table XI 
and the calculation of charging current for any assumed length of 
line, voltage, and wire spacing. 

^ Alternating Current Phenomena by Dr. C. P. Steinmetz. 



TRANSMISSION SYSTEM. 



141 



The values of charging current in Table XIII which are de- 
pendent upon a voltage between the line wires and the neutral 
point of 100,000 volts for a single mile of line at 25 cycles frequency 
and a given spacing are obtained by substitution in the formula 

(82). 

For example, assuming the conditions of the transmission 

problem above 

.0776 

= 0.0153 microfarad. (S^) 



C = 



2 logic' 



^«\.I02/ 

between i mile of No. 4 wire and neutral with 36 in. spacing 

2 TrfCE 

Ic=^^ (91) 

If I^= Charging current in amperes per mile at 100,000 volts 
f= Frequency in cycles per sec. 
C = Capacity in microfarads per mile. 
E = 100,000 volts. 

2 TT X 25 X 0.0153 ^ 100,000 



Ic = 



o. 239 amp. 



(91) 



10 

TABLE XIII. 
Charging Current of Single Wire in Amperes per Mile per 100,000 







Volts, 


25 Cycles. 


















Spacing in 


inches. 








Size wire 


















stranded. 
















1 


1 






24 


36 


48 


60 


72 

1 


84 


: 96 


' 108 


! 120 


i 150 


350000 cm. 


•329 


.300 


.283 


.270 


.261 


•254 


.248 


• 243 


•239 


.230 


300000 


.323 


•295 


.278 


.267 


.258 


.250 


• 245 


.240 


.236 


.227 


250000 


.316 


.290 


.274 


.262 


.253 


.246 


.241 


.236 


.232 


.224 


Solid 4/0 B & S 


.301 


.278 


.262 


•253 


•243 


•239 


.232 


.228 


.224 


.210 


3/0 


•295 


.272 


•257 


• 245 


•239 


•234 


.228 


.224 


.220 


.212 


2/0 


.287 


.265 


.251 


.242 


.232 


.228 


.224 


.220 


.217 


.209 





•279 


.261 


.246 


•237 


.229 


.225 


.220 


.217 


.212 


.206 


I 


.275 


•251 


.242 


.229 


.223 


.220 


.217 


.212 


.209 


.203 


2 


.268 


.250 


•237 


.226 


.221 


.217 


.212 


.209 


.206 


.199 


3 


.264 


.246 


.229 


.225 


.217 


.212 


.209 


.206 


• 203 


.196 


4 


•255 


.239 


.226 


.220 


.214 i 


.209 


.206 


.203 


.200 


•193 


6 


.245 


.231 


.220 


.212 


.204 1 

1 


.201 


.198 


• 195 


.191 


.189 



142 



ELECTRIC RAILWAY ENGINEERING. 



This value will be found in Table XIII opposite No. 4 wire with 
36 in. spacing. 

The charging current for any other voltage (E') between wire 
and neutral and for any other length of line (1) is of course 



I\ = 



2 TrfCEa 



'' 100,000 X 10® 



or 



r = 



Table value x 1 x E' 



100,000 



(92) 



(93) 



Again considering the concrete illustrative problem at unity 
power factor the charging current for the line is 



-r, 0.239x50x19,100 

I _ = =2. 28 amp. 

100,000 



(93) 



It will be seen therefore that the charging current with this par- 
ticular load and design of line is quite an appreciable percentage 
(8 . 7 per cent.) of the full load unity power factor current. The 
charging current might be decreased somewhat by separating 
the wires. As this current is independent of load its percentage 
will decrease of course as the load increases. 




I^X; 



Fig. 56. — ^Vector diagram for transmission line regulation with charging current. 

In refiguring the regulation this time taking the charging 
current into account, it must be remembered that this current 
leads the voltage at the substation (Eg) by 90 degrees. The 
vector diagram of voltages is therefore represented by Fig. 56 
where the direction of the charging current vector and therefore 
of the vector of resistance drop due to charging current (IcR) is 
vertical and the reactance drop due to charging current (I^XJ 



TRANSMISSION SYSTEM. 143 

horizontal since (Eg) is horizontal. The generator voltage (E''g) 
may be seen from the geometry of the diagram to be 

E", = V{E,+ I,,R- I,X,)H (I„X,+ I,Ry^ (94) 

which is obviously less than (Eg), equation (87), since the charg- 
ing current tends to neutralize the effect of line inductive re- 
actance, thereby reducing the regulation to the value 

Reg'' = "^^ (95) 

Substituting the numerical data of the above problem 



E^'g— \/(i9,ioo+26.2 X 65.4 — 2.28 X 15.5)^ + (26.2 X 15.5 + 
2.28 X 65.4)^ = 20,760 volts (94) 

20,760—19,100 

Resr'' = =8.7 per cent. (o c) 

19,100 ^^^^ 

A similar diagram might be drawn and the regulation calcu- 
lated showing the effect of charging current with low initial 
lagging power factor by adding the triangle of charging current 
fall of potential to the diagram, Fig. 55, with the vector (I^R) 
leading (EJ by 90 degrees. 

Comparing the regulation found by taking charging current 
into account equation (95), with that which neglected that partic- 
ular effect equation (88) the error will be seen to be 

9-8.7 

Error = = 1 . ^ per cent. 

8.7 

which may safely be neglected in most railway work, especially as 
the approximate method gives the highest and therefore the most 
conservative estimate of the regulation. 

It is believed that the above considerations, together with 
some of the suggestions regarding high tension line protection 
and wiring considered in Chapter III cover the more important 
factors involved in the design of high tension lines for railway 
service. For further details of construction and for theoretical 
consideration of the limiting factors which enter into exception- 
ally high voltage installations reference should be made to the 
many complete works on these subjects. 



144 ELECTRIC RA.ILWAY ENGINEERING. 

Estimates of construction costs on both distribution and trans- 
mission systems have been purposely omitted owing to the fact 
that the cost of copper is the dominating factor in these portions 
of the railway system and such cost is so variable a quantity that 
estimates or costs of previous installations have to be used with 
great caution when applying them to proposed systems. 



CHAPTER V. 
Power House Location and Design. 

Whereas the complete analysis of this subject would require a 
volume of generous dimensions, a few of the salient features to 
be borne in mind by the engineer in charge of the planning and 
construction of a complete electric railway system may well be 
suggested. 

Location. — The determination of the proper location for the 
power house from the one standpoint of most economical trans- 
mission of power to substations is made in a manner similar to 
that described for the location of substations, Chapter III, except 
that in this case the various loads are the full load ratings of the 
various substations supplied from the power station divided by 
the transmission line efficiency. The center of gravity of such 
loads spaced at the proper distance between substations locates 
the power station. 

With the power station, however, many other factors have 
to be considered before its location can be decided. The relative 
weight of these factors will vary with local conditions but they are 
listed below in the order of importance as nearly as can be deter- 
mined for the average case. 

The question of cheap coal supply to the steam power station 
is all important. In spite of this fact it is often neglected or 
given little thought, especially in the case of small stations, where 
it is often believed that coal may be drayed to the station at rela- 
tively small expense. The growth of traffic and competition with 
steam lines unwilling to cooperate with respect to the installation 
of spur tracks or track connections with the interurban road, have 
in a number of instances seriously embarrassed small interurban 
systems or at least prevented the power station reaching a reason- 
able cost of energy output. The station should be located on a 
railroad siding, or better, if the proposed line is in the vicinity of 
a navigable river, many of the other factors entering into the 
location of the station may be waived in order to locate the sta- 

lo 145 



146 ELECTRIC RAILWAY ENGINEERING. 

tion at a point where the coal may be deposited in the bunkers 
directly from the coal barges. A notable example of such loca- 
tion is that of the proposed power station of the southern in- 
terurban line previously referred to which is distant 3 miles 
from the line of the road in order that it may be located where 
ocean going coal barges may be docked. 

The question of an adequate and reasonably soft water supply 
for boiler feed and condensing purposes should receive second 
consideration. In sections of the country where it is necessary 
to depend upon artesian well water for boiler feed it is either 
necessary to install rather expensive water softening plants or 
submit to a high maintenance and depreciation charge on boilers 
with considerable risk of service interruption. The marked loss 
of efficiency and corresponding increase in cost of generated 
power if a condensing plant is occasionally forced to operate non- 
condensing is to be avoided if possible, especially in the case of 
steam turbines, whose principal advantage over the reciprocating 
engines is the increased economy at high degrees of condenser 
vacuum. Gravity intakes of pipe or concrete tunnel construc- 
tion are preferable to long pipe suction lines and considerable 
expense is warranted in bringing a generous supply of cold pure 
water into the cold wells of power stations and in providing 
a free discharge of the hot well to waste under all conditions of 
water level in flood season and drought. Especially should the 
purity of condensing water be assured with the surface type of 
condenser used to such an extent with steam turbines. 

Building foundations, especially for the heavy machinery of 
the station, should be unquestioned in their stability. Many 
instances may be quoted in which the saving of first costs of test 
borings or real estate was attempted at the later expense of the 
settling of foundations, carrying with it numberless construction 
and operating difficulties. Nor is it sufficient to determine the 
fact that there is good subsoil below a proposed station location. 
The depth of excavation necessary to reach this subsoil and the 
consequent cost of foundations should be carefully learned from 
preliminary test borings. 

The power station often acts in the capacity of one of the sub- 
stations on the line supplying the high tension lines to other sub- 



POWER HOUSE LOCATION AND DESIGN. 147 

Stations not only, but transforming a portion of the generated 
electrical energy into a forni adaptable to the nearby trolley 
and feeder system. This plan can only be carried out when 
the power station is located very near the right of way of the 
railroad as the low voltage of the distribution system is not 
designed for transmission to any considerable distance. 

The cost of real estate is a very obvious factor in the determina- 
tion of power station site. With an interurban road the center 
of gravity of the load would naturally remove the station from 
the terminal cities where the cost of real estate is probably higher 
than at any other point on the line, but the operation of the line 
or a portion of it at least by the existing power companies of the 
terminal cities often involves power station additions or new 
locations where real estate is high in cost. This sometimes leads 
to the double-decking of stations with turbine rooms above the 
boilers. This construction has the further advantage of short 
connections between boilers and turbines. 

A feature often overlooked in the selection of a site is the con- 
venience of a location near the car house and shops. Such a 
location often prevents a duplication of shop equipment and the 
tools, supplies, and even labor which may be used in common, 
especially in case of emergency, by both power station and car 
shops is surprising. Such cooperation between the departments 
of a large railway system must result in better service and im- 
proved economy of operation. 

Closely allied with the above is the necessity of locating the 
station at a point where employees and preferably some, if not all 
of the heads of departments, are willing to reside. Especially 
in the emergencies which are only too frequent in railway opera- 
tion is this of great value to the company. 

Within the city limits the question of smoke nuisance sometimes 
has a bearing upon the problem, but as expert firing and special 
design of furnaces with the possible installation of smoke consum- 
ing devices, if efficient ones can be obtained, reduce this trouble 
to an unobjectionable minimum, this factor has little weight in 
placing a station. 

Design. — The building which is to house the generating equip- 
ment should be designzed for that purpose primarily, without too 



148 



ELECTRIC RAILWAY ENGINEERING. 



much thought for architectural beauty. Too many small roads 
have elaborate stations which are paying little or no returns on 
the investment and are found wanting in highly efhcient equip- 
ment and attendance. Substantial brick or concrete buildings 
with generous basements for auxiliaries, piping, and wiring are 
necessary. They should be provided with plenty of head room 
for crane operation and generously lighted. Such a power sta- 
tion interior is illustrated in Fig. 57. This building is con- 
structed of concrete blocks and is well planned to house the single- 
phase generating equipment of the Chicago, Lake Shore, and 




Fig. 57. 



South Bend Railway, at Michigan City, Indiana.* This photo- 
graph was taken at night by means of the mercury vapor lamps 
used for illumination. 

The costs of power station buildings cover a wide range, but for 
a fairly large modern station sufficiently commodious to accom- 
date all necessary machinery without overcrowding a figure of 
from $3.25 to I3. 50 per square foot of floor area should be allowed. 

The question of vibration and foundation construction should 
be given very careful attention, especially where high speed 
reciprocating machinery is employed. Vibration has caused 
serious difiiculties even in turbine stations of the double-decked 
type with the turbines located on the second floor. Care should 
be taken also to plan for future extensions in the construction of 
the building, many stations being carried to the extreme of closing 



POWER HOUSE LOCATION AND DESIGN. 1 49 

one end with temporary corrugated iron" construction which may 
be readily torn down as extensions are made. 

Capacity. — In determining the total output of the station, 
methods similar to those used in the case of the substation are 
employed with due consideration being given to the "diversity 
factor." This factor, which has only recently been given its 
proper attention by operating companies, may be defined as the 
ratio of the maximum load on the station to the summation of the 
maximum loads of the various substations. That is to say, since 
the maximum loads come on the various substations at different 
times, the capacity of the power station may be considerably less 
than the sum of the substation capacities. The only accurate 
way, therefore, to determine the probable load on the power sta- 
tion is to plot the summation of all the substation load curves 
against the same abscissae of time and divide the average and 
maximum values of this load curve by the substation and trans- 
mission line efficiency. Such a load curve will involve, aside 
from its momentary fluctuations, two or more well defined peaks 
which must be taken into account in determining the number of 
units to be installed. Reference to Chapter III will recall the 
method of subdividing the total load into the proper number of 
generating units which is equally applicable to the power station, 
with the exception that extensive subdivision into a relatively 
large number of small units involves more small duplicate auxil- 
iary equipment in the case of the power station incurring corre- 
spondingly increased maintenance and attendance charges. The 
generating equipment of the average interurban power station 
will not include more than three units, one of which is often equal 
in capacity to the other two combined. 

Choice of Prime Movers. — When the transmission of power 
from a nearby water privilege with its relatively low cost of energy 
is not possible, the following methods of driving prime movers are 
usually open for consideration in laying out a new power station. 

1. Reciprocating steam engines. 

2. Steam turbines. 

3. Gas engines. 

4. Various combinations of the above. 

The relative advantages of the various prime movers and their 



ISO 



ELECTRIC RAILWAY ENGINEERING. 



combinations are best set forth by quoting Table XIV published 
by Mr. H. G. Scott. In this table the various maintenance 
charges of each type of installation are not only given their proper 
weights but the variation of the individual charges in changing 
from one prime mover to another are very clearly shown. In 
addition, the relative investments necessary for the various types 
of plant are compared with that for the reciprocating steam engine 
plant as loo per cent. 

TABLE XIV. 1 

Distribution of Maintenance and Operation Charges per Kw. Hour. 



Maintenance. 



Recip. 


Steam 


Eng. and 


Gas 


engines. 


turbines. 


turbines. 


engines. 


2.57 


0.51 


1-54 


2.57 


4.61 


4-30 


3-52 


i.iS 


0.58 


0.54 


0.44 


0. 29 


1 . 12 


1 . 12 


1 . 12 


1 . 12 


2 . 26 


2 . II 


1.74 


I-I3 


I 


06 


0.94 


0.80 


0.53 





74 


0.74 


0.74 


0.74 


7 


15 


6.68 


5.46 


1.79 





17 


0.17 


0.17 


0.17 


61 


30 


57.30 


46.87 


26.31 


7 


14 


0.71 


5.46 


3.57 


6 


71 


1-35 


4.03 


6.71 


I 


77 


0.35 


1 .01 


1.77 





30 


0.30 


0.30 


0.30 


2 


52 


2.52 


2.52 


2.52 


100 


00 


79.64 


75-72 


50.67 


100 


00 


82.50 


77.00 


100.00 



Gas en- 
gines and 
turbines. 



Engine room mechanical .... 

Boiler or producer room 

Coal and ash handling, appa- 
ratus 
Electrical apparatus 

Operation 

Coal and ash handling labor . 

Removal of ashes 

Dock rental 

Boiler room labor 

Boiler room oil, waste, etc . . . 

Coal 

Water 

Engine room mechanical labor. 

Lubrication 

Waste, etc 

Electrical labor 

Relative cost of maintenance 

and operation. 
Relative investment in per 

cent. 



46 



54 
95 
29 



13 
53 
74 
03 
17 
77 
14 
03 
06 
30 
52 
32 



91 . 20 



Attention should be called to the fact that companies that have 
been operating railway power stations with reciprocating engines 
are realizing the marked economy which can be obtained by 
introducing low pressure turbines between the low pressure 
cylinders of the engines and condensers and many such combina- 
tion engine and turbine stations are now in operation. The 
output of a condensing engine may be increased from 20 to 25 
per cent, in this way with but little extra space occupied and 
usually without building additions. 

^ Power Plant Economics by H. G. Scott, A. I. E. E., 1906. 



POWER HOUSE LOCATION AND DESIGN. 



I^I 




152 



ELECTRIC RAILWAY ENGINEERING. 



The status of low pressure turbine development may perhaps 
be best judged from the summary of the report of the Committee 
on Power Generation of the American Electric Railway Associa- 
tion in 1 910 which is quoted below as follows. 

"In general, the installation of low pressure turbines may be 
recommended wherever there are good engines installed, or in 
the case of a new installation where the load factor and the coal 
cost are high. In plants having a large installation of a good 
type of reciprocating engine the low pressure turbine may be 
added at a total cost, including new condenser, auxiliaries, 
foundations, piping, etc., of not to exceed $25.00 per kilowatt, 
thus bringing down the average overall investment per kilowatt 
of the entire plant and so reducing the fixed charges per kilowatt- 
hour." 

In deciding whether steam turbines or engines shall be installed 
the question of steam economy naturally receives first considera- 
tion. While comparative tests under exactly similar conditions 
have probably never been made and although it is necessary to 
make some assumptions in order to compare fairly the test 
results where operating conditions vary slightly, the following 
table from Kent's Mechanical Engineer's Handbook will prob- 
ably compare the two units with regard to economy as well as 
any. These values refer to a 600 h. p. horizontal turbine oper- 
ating with saturated steam at 150 lb. pressure and 28 in. vacuum 
and an 850 h. p. compound engine. These sizes of units are such 
as are often found in interurban power stations. 

TABLE XV. 

Comparative Steam Economy of Turbine and Compound 

Engine. 



Per cent, full load. 


41 


75 


100 


125 


Avg. 85 
per cent. 




Pounds water per brake h. p. 


600 h. p. turbine 


13.62 
13-78 


13-91 
13-44 


14.48 
13.66 


16.05 
17.36 


14. =;i 


850 h. p. compound engine. . . . 


14.56 



POWER HOUSE LOCATION AND DESIGN. 1 53 

A study of this table as well as other tests under nearly identical 
conditions indicates that there is little choice between the two 
units from the standpoint of economy alone. 

The turbine seems to be the unit most often selected at the 
present time, however, probably because of its advantages over 
the compound engine with regard to first cost, space occupied, uni- 
form rotation, freedom from vibration, low cost of foundations, etc. 

Steam Turbine. — If the steam turbine be decided upon the 
following items should be given particular attention in writing 
the specifications, in addition to the usual requirements of work- 
manship, grade of raw material, shipment, etc. Values will be 
substituted for a particular 1500 kw. specification in order that 
the requirements may be of more value for reference. 

Rating, 1500 kw. 2300 volts, 3-phase, 60 cycles. 

Multistage, condensing. 

Steam pressure, 150 lb. 

Back pressure, 2" referred to barometric pressure of 30'' 

at32°F. 

Superheat, 100° F. 

Excitation, 125 volts. 

Full load temperature rise at unity power factor, rated 

voltage, 40° C. corrected to room temperature of 25° C. 

Overload temperature rise, 125 per cent, load, rated 

voltage, unity power factor for 2 hr. 55° C, corrected to 

room temperature of 25° C. 

Momentary overload of 100 per cent, at rated voltage and 

unity power factor without injury. 

Economy expressed in lb. steam per kilowatt hour. 



Load per cent. 


EconoE 


50 


20.7 


75 


18.9 


100 


18.0 


150 


19.0 



Speed regulation at end of heat run, speed rise when unity 
power factor full load is suddenly thrown off shall not 
exceed 4 per cent, of normal full load speed. When 



154 ELECTRIC RAILWAY ENGINEERING. 

such load is gradually applied the speed variation shall 
not exceed 2 per cent, of normal full load speed. 
Voltage regulation at end of heat run when load is thrown 
off suddenly shall not exceed 188 volts. 
Insulation test shall be applied after heat run of 5000 
. volts alternating current for i min. between armature 
coils and surrounding conducting material and 1500 
volts alternating current for i min. between field wind- 
ing and surrounding conducting material. 
A non- condensing run shall be made with rated load, 
power factor, voltage, steam pressure, and superheat 
against atmospheric pressure. 

Vibration. — The units shall operate smoothly and with- 
out undue vibration and noise under all conditions, and 
all revolving parts shall be accurately balanced. 
Centrifugal Stresses. — The revolving field shall be suffi- 
ciently strong to resist for i min. without injury the 
centrifugal stresses produced by 20 per cent, excess 
of speed with armature and field circuits open. 

Steam Engine. — The features of particular importance in the 
steam engine specifications are found listed below, although these 
specifications do not refer to an engine for railway service. 

Type, horizontal, simple, side crank, designed to run 

"over." 

N on-condensing. 

Rating, 375 h. p. at most economical cut-ofT, at specified 

steam pressure, back pressure, and normal speed. 

Service, left hand direct connection to 250 kw. 2200 

volt, 3-phase, revolving field alternator. 

Speed, 200 r. p. m. 

Steam pressure to be 125 lb. dry steam at throttle. 

Back pressure to be 10 lb. 

Superheat, none. 

Overload, 50 per cent, for 2 hr., momentary overload 

of 100 per cent, without injury. 

Economy expressed in lb. steam per indicated h. p. hr. 

Speed regulation shall not exceed i 1/2 per cent, of nor- 



POWER HOUSE LOCATION AND DESIGN. 



155 



mal speed when full load is suddenly thrown on or off. 
The engine shall be designed to operate in such a man- 
ner that the alternating current generator to which it is 




MJ 



Fig. 59. 

connected will operate successfully in parallel with other 
alternators of like general type. 

Generator. — The consideration of the relative advantages of 
engine and turbine was purposely taken up first in order that the 



156 ELECTRIC RAILWAY ENGINEERING. 

necessity of installing a generator might be determined. If the 
steam engine be selected the alternating current direct connected 
generator will find a place in the power station equipment. 

It is of course necessary to know the generator efficiency in 
order to determine the brake horse power rating of the engine, 
the latter being found from the following equation 

Gen. output in kw x i. 34 
Eng. brake h. p. = ^^^^;^_ , (96) 

It is not only unnecessary but inadvisable to specify too close 
regulation for alternators in railway service. That the regulation 
need not be close has already been explained in connection with 
the transmission line design. In addition to that fact, however, 
it will be remembered that if close regulation be not required, the 
reactance and armature reaction of the alternator may be greater. 
This tends to protect the rrachine under the heavy overloads and 
short circuits to which it is likely to be subjected in railway 
service by lowering the voltage and therefore the short circuit 
current of the armature. The latter type of machines also has 
the further advantage of being able to keep in synchronism with 
one another more readily than those of better voltage regulating 
qualities. This is another valuable feature in railway power 
station operation. 

The specifications for such a machine are materially the same 
as for the generator portion of the turbine previously outlined, 
with the exception that the speed is reduced to from loo to 150 
r. p. m., and in some installations of small capacity a belted ex- 
citer is provided for each generator. 

Transformers. — The step-up transformers in the power station 
are identical with those discussed in detail in Chapter III, the 
low tension winding becoming the primary in this case. As in 
the case of the substation if the transmission line voltage does not 
exceed 13,000 volts, the generator armatures may be wound for 
full voltage and the transformers omitted. 

Transformer specifications should include the rating, frequency, 
primary and secondary voltages, type, i. e., whether oil, air, or 
water cooled, temperature rise (50° C.) on full load, provision for 
50 per cent, overload without undue heating for 2 hr., efficiency, 



POWER HOUSE LOCATION AND DESIGN. 1 57 

power factor of load, insulation test, regulation, etc. Such trans- 
formers as would be used in power station service might be ex- 
pected to have a regulation of 1.2 per cent., a full load efficiency 
of 98 per cent, or slightly more, and withstand a 10,000 volt 
insulation test for a 2200 volt rating. 

Switchboard. — This portion of the power station equipment 
is not materially different from that described in connection with 
substation design and that portion which may be installed to 
control substation apparatus in the power station is, of course, 
identical therewith. 

Above 13,000 volts and often below that voltage the board is 
of the remote control type with switches and usually cables and 
transformers as well, located in fire-proof brick or concrete cells. 
No protective device is installed between the generators and the 
bus bars, although the out-going transmission lines are protected 
with time limit relays, lightning arresters, and choke coils. For 
the purpose of synchronizing generators and in order to balance 
the loads properly between the various machines operating in 
parallel, the generator panels are often equipped with auxiliary 
circuit (125 volt) control devices for regulating the governors and 
thereby the speed of the prime movers. 

Exciters. — Although the individual alternators are occasion- 
ally provided with separate belt-driven exciters especially in small 
installations, it is customary to provide a steam-driven and 
usually a motor-driven exciter set, the former being necessary 
in starting a plant. As a considerable amount of 125 volt direct 
current power is used about the station for auxiliary control cir- 
cuits, etc., the exciters should be considerably larger than the 
combined demands of all alternator fields which they are called 
upon to supply. In selecting the exciter capacity it should also be 
borne in mind that the generators at low power factor require con- 
siderably increased excitation to maintain normal voltage at full 
load and the exciter should, therefore, be sufficiently large to 
supply this demand. As an additional protection against failure 
of excitation current which is the back bone of the power plant, 
storage batteries are often ''floated" on the 125 volt bus bars, 
ready to supply energy to the field windings in case of failure of 
the exciters. 



158 



ELECTRIC RAILWAY ENGINEERING. 




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spiS jaonpoaj 



POWER HOUSE LOCATION AND DESIGN. 1 59 

Condensers. — As most railway power stations are operated 
condensing, especially when turbines are installed, the various 
types of condensers must be compared and a selection made of the 
most suitable for the purpose at hand. Condensers may be read- 
ily subdivided into three classes. 

Jet condensers are designed to spray the condensing water into 
the steam as it comes from the low pressure cylinder of the engine, 
the steam coming in direct contact with the water. This type 
is extremely simple and cheap in first cost but in cases where the 
condensing water is unsuitable for boiler feed and water for the 
latter purpose is expensive, the jet condenser is uneconomical by 
reason of its wasting the condensed steam which might otherwise 
be used again in the boilers. The heat in the exhaust steam is 
also lost in this case. Pumps are provided with the condenser 
for supplying water and extracting air and water from the con- 
densing chamber and thereby maintaining a vacuum. The 
former pump in large installations is usually of the centrifugal 
type. 

Barometric condensers depend upon the principle that atmos- 
pheric pressure will maintain a column of water 34 ft. in height 
in the tail pipe of the condenser between the condenser head and 
the hot well. This' necessitates mounting the condenser chamber 
34 ft. above the hot well which often brings this chamber above 
the roof of the power house. The exhaust steam from the engine 
is discharged into this chamber and two pumps discharge water 
into and extract air from this chamber respectively. The vacuum 
is maintained by the syphon action of the column of water while 
simply the air which is entrained in the condensing water is 
removed by the air pump and the vacuum thereby improved. 
This type of condenser is intermediate between the other two 
types in expense but is usually capable of maintaining a better 
vacuum than the jet type. It is subject to the same disadvantages 
from the standpoint of feed water economy as the jet condenser. 

Surface Condenser. — This condenser is the most expensive of 
the three types, involving as it does a series of tubes mounted 
within a cast iron shell, the condensing water circulating through 
the tubes and the steam entering and being condensed in the 
outside shell. As the condensed steam and condensing water 



l6o ELECTRIC RAILWAY ENGINEERING. 

do not come in contact with one another the former may be 
used again as feed water and its initial heat used to advantage. 
Air and water circulating pumps are used as in the previous types. 
Whereas a better vacuum can be obtained with a surface con- 
denser its maintenance and tube depreciation are high. It is 
not in extensive use, therefore, except with steam turbines where 
the slight gain in vacuum is of greatest importance. 

The amount of water required for condensing purposes and 
therefore the si^e of condenser and piping necessary are readily 
calculated from the thermodynamic equation 

H-h 

W = ,j^ (97) 

where W = Weight of condensing water in pounds. 

H = Total heat in steam at the pressure corresponding to 

exhaust. 
h =Heat in water at temperature of air pump discharge. 
T = Temperature of discharged condensing water in de- 
grees Fahrenheit, 
t = Temperature of the entering condesing water. 

The above values may be readily obtained from the steam 
tables but a rough approximation of (W) may be made by as- 
suming average values of the above units as follows: 

W=ii5o, h=i20, T=iio, and t=7o 
Whence 

II50— I20 

W = = 25.8 lb. water necessary to condense each pound 

40 

of steam. 

Total water necessary per h. p. hr. is 

"Wi^ = W x (Eng. economy in pounds steam per h. p. hr.) (98) 
Multiplying by the rated indicated h. p. of the engine the con- 
densing water in pounds per hour is determined. 

It is customary to use a factor of safety above this figure and 
while 30 lb. of water per h.p. hour is a figure often quoted, 
many engineers install condensers and pumps on the basis of 
40 lb. water per h. p. hour. In writing specifications for con- 
densers it is the usual practice to refer to the water rate of the 
engine, its operating pressures and the probable water temper- 



POWER HOUSE LOCATION AND DESIGN. 



l6l 




IsnBqxg^ 



II 



l62 ELECTRIC RAILWAY ENGINEERING. 

atures, and require the manufacturers to furnish a condenser 

sufficiently large to maintain the vacuum most economically. 

Boilers. — Knowing the amount of water required per hour 

by the engines or turbines, the specified water rate of the auxiliary 

pumps may be added directly or in some cases the assumption 

may be made that the auxiliaries will take from 2.5 to 5 per cent. 

of the steam taken by the engines. A boiler h. p. is defined as 

"the evaporation of 34.5 lb. of water from and at 212° F. per 

hour." The boiler rating may now be determined from the 

equation 

•. W(Xr+q-qJ 

Boiler h. p. = (go) 

34-5 
where 

W = Steam consumption of engines and auxiliaries per hour 
in pounds. 

X = Percentage of (W) which is dry steam. 

r = Heat of vaporization of steam at absolute boiler pressure 
from steam tables. 

q =Heat of liquid at boiler pressure from steam tables. 

q^ =Heat of liquid at feed- water temperature from steam 
tables. 

If proper consideration has been given to the overloads de- 
manded at different times of day and during the various seasons 
of the year and provision made for a sufficient number of boilers, 
being constantly out of service to guarantee plenty of time for 
cleaning, the capacity of the boiler plant may be based on the 
above equation, the size of the units being the next standard size 
above that given by the above equation. The largest capacity 
installed in a single unit is 500 h. p. 

Boilers are broadly classified as water-tube and fire-tube, with 
a large number of varying designs under each classification. In 
spite of the fact that the water-tube boiler is the most expensive, 
it is rather generally installed in railway plants largely because 
of its ability to steam quickly under the sudden overloads that are 
experienced in railway practice. 

Steam boilers require a special foundation with ash pits opening 
below the boiler room floor, usually into some type of ash con- 
veying machinery. The boiler drums and tubes are freely sup- 



POWER HOUSE LOCATION AND DESIGN. 1 63 

ported from a steel frame in such a manner that they may readily 
expand with the rise in temperature. The setting, consisting of 
fire brick arches and walls surrounded by outside walls of com- 
mon brick, completes the installation. 

Boiler specifications should cover the following features: 

Rating in boiler horse power. 

Steam pressure. 

Setting, single or in batteries. 

Type of support, suspension or wall. 

Size of steam and blow-off outlet and feed water inlet. 

Grate area. 

Safety-valve, gauges, and feed check valve. 

Weight and size of breeching to stack. 

Arrangement of arches. 

Hydrostatic test. 

Mechanical stokers for the automatic feeding of coal from the 
bunkers to the furnaces are generally installed in larger plants. 
They enable one fireman to care for several more boilers than 
with hand firing and reduce the temperature of the boiler room 
considerably. 

Feed Water Heaters. — Reference to equation (99) will show 
that if the initial temperature of the feed water entering the 
boilers (qo) be raised, the boiler horse power required for a given 
duty will be less. Add to this the lessened strain on boiler tubes 
and plates when warm water is fed to the boiler in place of cold 
and the further fact that this rise in temperature may be obtained 
by the use of heat in exhaust steam from auxiliaries or from the 
engine itself if operating non-condensing and the economy of 
installing a feed-water heater will be at once apparent. Such 
devices are therefore commonly installed in the boiler room and 
raise the temperature of the feed water to 200 or 212° F. before 
it enters the boiler. The feed-water heater may be either the 
open type operating at atmospheric pressure or the closed type 
in which the water is forced through the heater by the feed pump 
under boiler pressure. Provision is made in the heater for readily 
cleaning from same the scale often deposited by water containing 
mineral salts and in many installations the water-softening 
apparatus of the hot-water type is combined with the heater to 



164 ELECTRIC RAILWAY ENGINEERING. 

remove the scale forming chemicals and heat the water in one 
operation. Specifications need include only the boiler horse power 
supplied, the boiler pressure, the average normal feed-water tem- 
perature, and the approximate amount of exhaust steam available 
for heating purposes. If the apparatus is to include water- 
softening equipment, an analysis of the feed water or a sample of 
same must accompany the specifications. 

Feed Pumps. — Steam driven reciprocating feed pumps of 
double the capacity necessary to furnish the boiler feed water 
maximum overload should be installed so that repairs may be 
made at any time without crippling the service. As the feed 
water supply is the back bone of the boiler plant its design should 
be carefully studied and generously provided for. The water 
should flow to the suction of the feed pumps by gravity if possible. 

Draft. — ^^Although mechanical draft of the forced or induced 
type is resorted to in some installations, the natural draft pro- 
duced by chimneys is by far the most common. A single stack 
is usually sufficient for a medium size plant. If the use of in- 
ferior grades of coal is contemplated because of their low cost the 
draft provided must be correspondingly great. As the draft 
produced by a chimney is dependent upon its height, Mr. J. J. 
DeKinder advises that the following heights of chimneys be 
adopted for the various grades of coal. 

TABLE XVI. 

Heights of Chimneys for Various Grades of Coal. 



Coal. 



Height in feet. 



Free burning bituminous coal. . 
Slow burning bituminous slack. 
Slow burning bituminous coal. . 

Anthracite pea coal 

Anthracite buckwheat coal 



75 
100 

115 
125 
150 



As the formulae used in chimney design involve the height and 
area and as the capacity in boiler horse power for which a 
chimney can supply draft is proportional to the latter factor, it 



POWER HOUSE LOCATION AND DESIGN. 1 65 

is well to assume the height first for the degree of draft required 

and the type of coal used and calculate the necessary area of cross 

section from formula (100). Occasionally the reverse process 

may be more desirable. 

Kent's formula for chimney design which is commonly used is 

Boiler h. p. 

E= -^ (100) 

3-33 \/H 

where 

E = Effective area of cross section. 

H = Height in feet. 

Chimneys of small dimensions are sometimes constructed of 
sheet iron but in larger designs are either' common brick, Custodis 
radial brick, or concrete. Linings are provided generally for one- 
half or the entire height depending upon the temperature of the 
flue gases, but care must be taken to have the lining entirely inde- 
pendent of the outside walls to avoid troubles from expansion 
and contraction. 

That the cost of chimneys is an item of some consequence in 
the first cost of the power plant, especially in the case of tall 
ornamental chimneys, will be noted from the costs and estimates 
which follow. 

Coal and Ash Handling Machinery. — The judgment of the 
consulting engineer must be exercised in determining the extent 
to which coal and ashes shall be handled mechanically in a plant 
of given size. Where mechanical stokers are used, some type of 
coal and ash handling machinery is generally found, usually the 
continuous belt, bucket type of apparatus used for the two pur- 
poses of removing ashes from under the boilers to the outside of 
the station or to empty cars on the railway siding and also taking 
coal from the crushers and delivering it to the overhead bunkers. 
In some installations ash cars running longitudinally under the 
boiler room floor convey ashes from the boilers to an elevator 
shaft and thence outside the building, while the same cars and 
elevator are used for coal hoisting. This is cheaper in first cost 
but more expensive to operate than the former type. In large 
stations on the water front additional equipment is found for 
raising coal from the holds of coal barges to the crushing machines. 

In any event the coal and ash handling machinery, commonly 



1 66 



ELECTRIC RAILWAY ENGINEERING. 



electrically operated, is expensive in first cost. It reduces the 
operating charges, however, and it is therefore necessary to bal- 
ance the fixed charges of its installation against the saving in 
operating cost, in order to determine whether or not its installa- 
tion is warranted. 

Arrangement of Equipment. — The most convenient arrange- 
ment of apparatus and wiring in a power station is greatly influ- 
enced by local conditions. A good idea of such arrangement may 



Reinforced Cinder Concrete 




ZZZZ22ZZ2ZZ22 Si 



Concrete 



fer.-J 



^ndenser^ Room 




Cbimney 
180 X 12'Dia. 



be obtained from Fig. 58 which represents a transverse section 
through the boiler and engine room of a typical power station 
using reciprocating engines direct connected to alternators, water- 
tube boilers, and jet condensers. A similar section thjrough the 
high tension switch house is shown in Fig. 59. A plan view 
of a gas engine station will be found in Fig. 60, while Fig. 61 
shows a section of the turbine station of the Indianapolis and 
Cincinnati Railway Company at Rushville, Indiana. 



POWER HOUSE LOCATION AND DESIGN. 



167 



Cost of Power Station Equipped. — Complete power stations 
including buildings, but not cost of land, may be estimated to cost 
between Sioo and Si 50 per kilowatt of rated output, depending 
upon the elaborateness of design and the addition of mechanical 
labor saving and safety devices. Occasionally the above minimum 
figure may be greatly reduced, as was the case of the rather unique 
double-decked station of the Fort Wayne and Northern Indiana 
Railway Company, Fig. 62, located in Fort Wayne, Indiana, 
whose detailed costs listed in Table XVII are taken from a paper 
before the American Street and Interurban Railway Association 
by Mr. J. R. Bibbins. 



TABLE XVII. 
Cost of Completed Power Station. 8500 Kw. No Substation Apparatus. 



Total cost. 


Cost per kw. 


Building: Including general concrete and steel work, 


$93 > 2 17 


$10.97 


galleries, coal bunker, smoke flue, condenser pit. 






coal-storage pit, etc. 






Generating Plants Including turbine, generators, ex- 


259,711 


30-55 


citers, cables, switch-board, transformers, and 






ventilating ducts. 






Boiler Plant: Including boilers, superheaters, stokers, 


118,313 


13.92 


piping, pumps, heaters, settings, breechings, and 






tank. 






Condenser Plant: Including condensers, pumps, free 


33,790 


3 98 


exhaust, water tunnels, and intake screen. 






Coal Handling Plant: Including gantry crane, crusher, 


7>99o 


0.94 


motors, and track. 






Erection, superintendence, engineering, and miscel- 


5o>5oo 


5-94 


laneous. 










$563,520 


$66 . 25 



In contrast to the above double-decked station there may be 
found listed below the final estimate exclusive of land for a 
modern interurban power station in the south of 2000 kw. 
rated capacity involving substation equipment of 300 kw. 
capacity. This estimate is given in considerable detail as it is 
believed it will be of value in determining the relative costs of the 



1 68 



ELECTRIC RAILWAY ENGINEERING. 



various portions of the equipment, even if the actual prices do 
vary, as they must from time to time. While the cost has been 
reduced to a kilowatt basis it should be stated that the estimates 
are frqm detailed figures based upon actual quotations, the 
values per kilowatt being results of the estimate and not the basis 
thereof. 



Estimate for Complete Interueban Power Station 2000 Kw. Rating with 
300 Kw. Substation Equipment. 



Total 
cost 



Cost per 
kw. 



Surveying and clearing site 

Excavating and Grading 10,000 yd. 



25 cents. 



Btiilding proper, 12,000 sq. ft. ©$3.25 

Machinery foundations, 2 turbine foundations, 100 yd. 

@ $10 

I Stack foundation, 200 yd. @ $8 

2400 h. p. Boiler foundation, @ i . 60 h. p 

2400 h. p. Boiler settings @ 2 . 60 h. p 

Miscellaneous foundations, 100 yd. @ 10 



Stacks and Flues, i stack g'xiSo' (Custodis) 

2400 h. p. flues @ 1 .00 h. p 

Dampers, Regtilators, etc 



Coal and ash handling apparatus, locomotive crane. 

Conveyor, crusher and scales 

Ash cars and track 

Ash pit 

Storage yard tracks, etc 

Conveyor trestle 



Cranes, lighting, plumbing, etc.. Crane. 

Lighting, 

Plumbing 

Gratings, railings, etc 



Wells, intakes, etc 

Boilers, stokers, etc., boilers, 2400 h. p. ( 
Stokers, 2400 h. p. @ 5.00 erected. 



15 . 50 erected. 



Piping, valves, etc 

Steam turbines, Curtiss turbines 2-1000 kw. 
Frt. and starting 



Auxiliaries, Heater, 1800 h. p. 
Condensers, 2 @ $5,500. . 
Feed pumps, 2 @ 1,100. . 
Fire pump, i @ 1,100. . . . 

Oiling system 

Freight and erection 



$300 
2500 



1000 
1600 
3850 
6250 
1000 

8000 
2400 
1000 

9000 
7500 
600 
500 
1500 
1000 

5000 
1500 
1000 
1000 



37200 
12000 



60000 
3000 

900 

IIOOO 

2200 
1 100 
1500 
2000 



2,SOO 
39,000 



13,700 



11,400 



20,100 

8,500 
20,000 
49,200 
23,000 
63 000 



18,700 



1.40 
19-50 



6.8s 



S-70 



10.05 



4-25 
10.00 
24.60 
II .50 
31-50 



9-35 



POWER HOUSE LOCATION AND DESIGN. 



169 



Estimate for Complete Interurban Power Station 2000 Kw. Rating with 
300 Kw. Substation Equipment. — Continued. 



Total 
cost 



Cost per 
kw. 



Generators, exciters, rotaries, etc., Rotary converter, 

300 kw. @ $16.00 

Transformers, 480 kw. @ 10.00 

Turbine exciters, 2—35 kw 

Motor-generator set, Ltg. 100 kw. ©40.00 

Frt. and erection 



Switchboards and wiring, 16 panels. 

3 blank panels 

Miscellaneous brackets, etc. ... 

Frt. and erection 

Wiring @ $1.50 per kw 

Switch cells 



Miscellaneous 

Sundry supplies and expenses. 



4800 
4800 
3600 
4000 
2000 

7900 
ISO 
ISO 
1000 
3000 
1000 



19,200 



13,200 



2,500 
2.500 



9.60 



6.60 
I 25 

1-25 



Grand total exclusive of land and engineering salaries 
and commissions. 



504,300 



)I52.00 



CHAPTER VI. 
Bonds and Bonding. 

The circuit which supplies current from the substation to the 
car has already been outlined. The return portion of this circuit 
is made up of the track rails, being augmented by return copper 
feeders in parallel with the track only incases of heaviest service. 
As rail lengths of either 30 or 60 ft. are used a single rail will have 
SS or 176 points per mile at which the electrical resistance of the 
connection between rails made by means of corroded fish plates 
would normally be very high. With this high resistance directly 
in series with the return circuit, any reasonable addition to the 
copper in the positive feeders is of little value. It was quickly 
found, therefore, in the operation of the early railway systems 
that the ends of rails must be connected electrically by conductors 
of lower resistance than the fish plates. These conductors have 
been designated as ''bonds." 

In the first installations bare copper negative return wires were 
laid along the ties between the rails and connected with the center 
of each length of rail with a copper wire. This method, however, 
proved very expensive and was abandoned, although it has been 
reinstated recently of necessity in similar form where traffic is 
very heavy, particularly in city systems. Later the ends of rails 
were bonded by means of No. 6 galvanized wire bonds clamped 
under the heads of track bolts. Such bonds were not only soon 
destroyed by galvanic action in the earth but were found to be of 
such high resistance as to be of little use. A slight decrease in 
the contact resistance of these bonds was later affected by forcing 
the bond wires into holes drilled in the heads of the bolts. The 
inability to reduce the track resistance sufficiently by any of the 
above means led to the introduction of the solid copper bond 
which in turn developed into the laminated strip copper and 
stranded copper bonds which are preferable because of their 
flexibility. 

Several distinctive types of the latter bonds have now come into 

170 



BONDS AND BONDING. 171 

very general use and a brief description of each will therefore be 
found below. 

Compressed Terminal Bonds. — This type of terminal has 
been applied to various designs of copper bonds. It consists of a 
cylindrical head varying from 5/8 in. to i in. in diameter and 
slightly longer than the thickness of the web of the rail. This head 
is forced into a recently reamed hole in the web of the rail by means 
of a heavy screw clamp provided with a conical contact which 
engages the center of the bond head and causes it to expand and 
flow under the pressure applied so that it makes intimate contact 
with the inner surface of the hole and heads over, rivet like, so as 
to prevent easy loosening or removal. Some compressed terminal 
bonds have their heads drilled with an axial hole through which a 
tapered steel pin in driven in order to expand the copper head 
well into the hole in the web. 

Compressed terminal bonds may be installed so as to surround 
the fish plate or they may be of the "protected" type, installed 
before the fish plates are put on and later covered by the latter 
plates, thus protecting the bond from mechanical injury or theft. 
When installing this bond great care must be exercised not to 
drill the holes much before the bonds are inserted and to use a 
lubricant when drilling holes which will not produce an insulating 
film on the inside surface of the hole. Clear water or a solution 
of bicarbonate of soda and water may be used but oil and soapy 
water should not be tolerated as lubricants. 

Soldered or Brazed Bonds. — Bonds similar to the above but 
with flat tinned heads are sometimes soldered or brazed to the 
side of the rail head or under the rail flange by means of a gasoline 
or oxy-hydrogen blow-torch after the rail has been brightened at 
the point of contact. These bonds have not proved entirely 
satisfactory, however, as they are quite likely to work loose and 
are also quite easily stolen. 

Electrically Welded Bonds. — A process of electrically welding 
a short laminated copper bond, provided with a brass head, upon 
the sides of the rail heads has recently been developed. This is 
accomplished by the use of a very large alternating current passing 
through the very small areas of bond, rail head, and carbon ter- 
minal in series and thus bringing the two metals to a welding heat. 



172 



ELECTRIC RAILWAY ENGINEERING. 



While this process is termed welding it is more correctly brazing, 
since two different metals are joined with a flux of borax between. 
The large alternating current necessary is produced by making 
the yoke and jaws which grip the bond and rail head a part of the 
secondary circuit of a current transformer whose primary is 
supplied from the alternating current side of an inverted syn- 
chronous converter. This converter is mounted on the car which 
carries the bonding outfit and is supplied with direct current 




Fig. 63. 



from the trolley. The ratio of transformation and impednace of 
the transformer secondary circuit are such that the current flowing 
through the weld is in the neighborhood of 1000 amperes. The 
particular equipment from which these values were obtained, 
Fig. 63, involves a 15 kw. transformer supplied from and 18 kw. 
inverted synchronous converter operating at a frequency of 
25 cycles. The transformer was connected for two voltages of 
375 and 500 volts respectively, while the secondary voltage varied 
from one to seven volts. The converter was also used as a motor 
to propel the car. 



BONDS AND BONDING. 173 

In this particular test^ with the 500 volt connection, the time 
required to make a weld averaged 82 sec. with an input to the 
car per bond of 797 watt hours. An estimate of the cost of 
electric welding, assuming that 40 welds per day can be made 
would, therefore, result as follows, if power costs 2.5 cents per 
kilowatt hour at the car. 

Cost of energy o . 797X . 025 $ . 019 

Cost of bond 30 

Cost of labor 112 

Sundries 01 



$.441 



This estimate is slightly low since it is always necessary to grind 
a bright place on the head of the rail before the bond is applied. 
This is accomplished by means of an electric motor-driven grinder 
connected with the trolley. The power for this purpose was not 
included in the above estimate, although a labor item was allowed 
to cover the work. It is safe to say, however, that these bonds 
may be installed for 45 cents each while the other types vary from 
something less than this up to 70 cents, each installed. 

Amalgam Bonds. — Bonds consisting of semiplastic amalgam 
forced between the brightened surfaces of rail web and fish plate 
are occasionally found, although not in common use. 

Aside from the above, several methods of making continuous 
rail joints of high electrical conductivity may well be classified 
under the heading of bonds. Such methods in common use are as 
follows: 

Cast Welded Joint. — In making this joint, melted iron of 
special composition and high conductivity is poured around the 
rail ends, with the exception of the heads, while they are enclosed 
in a sand or iron mould of such shape as to leave a heavy lug of 
cast iron about the ends of the rail. While it is rather difficult 
with this process to raise the temperature of the rail quickly 
enough to insure molecular adhesion between the rail and the 
molten metal, yet very satisfactory results have been obtained in 
many instances from both the standpoints of electrical conduc- 
tivity and mechanical rigidity. 

^ Thesis, Purdue University, 1910, by Broadwell, Cole, and Stevenson. 



174 ELECTRIC RAILWAY ENGINEERING. 

Thermit Welded Joint. — A combined joint and bond of com- 
paratively recent origin is produced by the ^' thermit " process. As 
in the previous method a mould of sand is made about the rail 
ends but in this case only sufficient thermit for one joint is melted 
at a time. This melting is accomplished by making use of the 
well known fact that finely divided aluminum when oxydized 
develops a great amount of heat. This reaction has been recently 
brought under control so that a small amount of powdered alumi- 
num mixed with iron oxide, if ignited with a small amount of 
ignition mixture, will react as above explained with sufficient heat 
to melt the iron which in turn is poured about the rail ends. This 
produces a joint similar to the cast weld with less metal but with 
apparently quite as good electrical and mechanical characteristics. 

Electric Welded Joint. — In contrast to the electric welded 
bond mentioned above there may be found in the city tracks of 
many railway companies the electric welded rail joint. This, a 
rigid rail joint, produced by electrically welding heavy iron bars 
on either side of the webs of adjacent rail ends, should be carefully 
differentiated from the electric welded bond, although the proc- 
ess of welding is almost identical with that outlined above, with 
the exception that iron only is used and the size of weld and corre- 
sponding power used are much greater. In this latter type of 
joint iron filler blocks are inserted between the rail ends and 
ground to the form of the rail head so that the joint is entirely 
closed and the operation of cars over rail joints is made so much 
the smoother. This joint has given very satisfactory service both 
electrically as a bond, for its conductivity is practically equal to 
that of the rail, and mechanically as a rail joint, the breakages 
not exceeding i per cent, of the total joints welded after several 
years of service in at least one installation and averaging very 
close to this record on several other roads. 

When considering any of these three methods of making combi- 
nation rail joints and bonds where the joint is necessarily mechan- 
ically rigid, it should be borne in mind that the track will expand 
in hot weather sufficiently to throw it noticeably out of gauge 
if it is not rigidly held in place by street paving. None of these 
methods are therefore suitable for anything but paved city streets, 
unless an exception be made of the few cases where they have 



BONDS AND BONDING. 



175 



been tried with expansion joints every few hundred feet. At 
these joints of course some other type of bond must necessarily be 
installed. 

As these processes combine a rail joint with a bond, doing away 
with fish plates, track bolts, and other types of bonds, their expense 
is naturally much greater than that of any other bond alone. 
^Herrick and Boynton give average prices for these combined 



Voltmeter 



t Ac. Side Rotary 




Dc. Side Rotary 




Voltmeter 



Special Current 
Transformer 



O 



^ Connected to Bond Clamps 
Fig. 64. — Connections for electric welding of bonds. 



joints of from $2.67 each for cast welded joints and $4.50 each for 
the "Thermit" process, up to I5.50 or $6.00 per joint for the 
electric weld. These figures do not include opening and closing 
the pavement around the joint in case old track is being treated, 
which cost will vary from Si. 00 to $1.25 per joint. 

Bond Testing. — The bond resistance of a well bonded track 
using 4/0 B & S bonds will range from 5 to 7 per cent, of the 
resistance of the track return. With a few missing bonds or 
with poor contacts between bonds and rails this resistance may 

^ American Electric Railway Practice, by Herrick and Boynton. 



176 ELECTRIC RAILWAY ENGINEERING. 

be increased many times. While the maximum allowable 
voltage drop in the return circuit is often very rigidly fixed in the 
city systems by municipal ordinance, it is for the interest of the 
operating company to keep this resistance at a minmium value, 
since the voltage at the car varies inversely and the losses vary 
directly with the resistance. It has been customary, therefore, to 
make frequent tests of the resistance of rail bonds and the stand- 
ard has been rather arbitrarily set that the resistance of a bond 
shall be less than that of 3 ft. of rail. 

The comparison of the resistance of the bond with that of 3 ft. 
rail may be very readily made by making use of the cui:rent 



r<D- 



a 



_ik_ 



o o ;; o o 



Fig. 65. — Connections of bond testing meters. 

flowing in the rail. Two contacts, (a) and (b) Fig. 65, consisting 
of hardened steel knife edges or points connected to a milli- 
voltmeter (V) are applied to the head of the rail at a distance apart 
corresponding to the length of the bond. A third contact (c) is 
permanently spaced 3 ft. distant from one of the former contacts, 
(b). If another milli- voltmeter (V) be connected between (b) 
and (c) and read simultaneously with the meter connected to (a) 
and (b) the readings are proportional to the resistance of a 3-ft. 
section of rail and that of the bond respectively. The bond may 
be pronounced in satisfactory condition if 

\<V' (loi) 

while if (V) be too great its departure from the required value 

may be recorded as 

ioo(V-VO 

percent. (102) 

Care must be exercised in making these tests not to damage 
the milli-voltmeter by attempting to measure an open bond. 
It is always well to try the bond on a meter with a 15 volt scale 
first and if the drop in potential is found to be within the range 



BONDS AND BONDING. 177 

of the milli-voltmeter to make the final reading with the latter 
instrument. 

As this process is a rather slow and tedious one where there 
are a large number of bonds to be tested, various methods have 
been devised for making the tests on a car as the latter is traveling 
over the road. Usually this is necessarily done when the regular 
cars are off the line at night or with very little varying current in 
the rails. The current sufficient to determine the voltage drop 
in rail sections and bonds is fed through the local rail section by 
means of specially designed trucks, the current being controlled 
by a rheostat on the test car. ^ 

If it be desired to learn only the total resistance of the track 
return this may be determined after the cars are off a section of 
line by passing a measured current through the rails by means of 
a feeder to the distant end of the line and a rheostat at that point 
in series therewith. A second feeder may be disconnected from 
the generator temporarily and used as a potential lead so that the 
fall in potential in the track may be read upon a voltmeter in the 
power house. 

Cross Bonding. — Thus far the bonding of rail ends alone has 
been considered. It is sometimes necessary to provide against 
the greatly increased resistance of the return circuit due to a 
possible open bond by connecting the rails together electrically 
by means of cross bonds spaced several hundred feet apart. 
These usually consist of bare copper wire of approximately the 
size of the bonds soldered to the bonds on opposite rails or to 
special single headed bond terminals forced into the rail web. 
Thus if a bond be open, the return current on that particular 
rail would follow the nearest cross bond to the other rail and find 
its way back to the original rail at the next cross bond nearest the 
power station. 

As the bonding of all joints in special track work such as 
switches, cross-overs, and frogs would often involve a large number 
of bonds, a heavy cable is often laid around such portions of the 
track and thoroughly bonded to the sections of track on either 
side thereof. 

^ Practical Electric Railway Handbook by Herrick. 



12 



CHAPTER VII. 
Electrolysis. 

The subject of the electrolysis of underground pipe systems is 
so closely allied to that of bonding that no sharply defined line 
can be drawn between them. Beginning with the rather general 
introduction of the direct current street railway systems in the 
early nineties, with their track return and relatively poor bond- 
ing, and extending through the rapid development and improve- 
ment of such systems, the question of electrolysis, its cause and 
prevention, has maintained an important although ever decreas- 
ing prominence in the studies and discussions of the engineers of 
gas and water works corporations as well as the telephone and 
street railway interests. 

It has, of course, been known for a long time that if a direct 
current be allowed to flow from a metal electrode, through an 
electrolyte to a second metal electrode, a chemical reaction takes 
place at the expense of the positive plate, i.e., this plate is actually 
eaten away, the metal removed therefrom forming a salt with 
some of the acid radicals of the electrolyte. During these reac- 
tions which take place similarly when moist earth is the electro- 
lyte it was noticed that hydrogen was given off at the cathode or 
negative terminal while oxygen was liberated at the anode. It 
was supposed for some time that those free gases were formed 
from the decomposition of the water in the earth. When it was 
later found, however, that this action often took place with poten- 
tials between terminals of the order of hundredths and even 
thousandths of a volt, which are not sufficient to decompose water 
and free these gases at their respective electrodes, a further study of 
the problem was undertaken. 

Experiments carried on at the University of Wisconsin and 
recorded in the discussion of a very able paper upon this subject 
presented before the American Institute of Electrical Engineers 
by the late Isaiah H. Farnham in 1894 demonstrated the fact that 

178 



ELECTROLYSIS. 1 79 

with iron electrodes embedded in moist earth electrochemical 
action is substantially as follows: Most earths contain salts of 
alkaline metals. Merely a directive electromotive force of the 
order of .001 volt will cause the acid radical of these salts to be 
isolated. This radical then attacks the anode. Suppose sodium 
sulphate (NaSOJ be present in the earth; this is broken up by 
the current into (Na) and (SO J. The SO^ forms with the posi- 
tive iron electrode (FeSO J while the hydroxide of sodium (NaOH) 
is formed at the cathode. When the earth in the neighborhood of 
the terminals becomes saturated with these compounds they dif- 
fuse toward one another and finally meet in the earth at a point 
easily detected by the formation of a green precipitate of ferrous 
hydroxide and the original salt. This reaction causes a local rise 
in temperature at the point where the precipitate forms. The 
reactions mentioned above, which take place at the electrodes, 
release oxygen gas at the anode and hydrogen at the cathode, the 
former resulting from an excess of SO^ forming an acid with the 
hydrogen of the water and setting oxygen free. The latter is the 
result of the formation of the hydroxide of sodium with water; 
the free atom of hydrogen from the water being liberated. 

The one point of practical interest in this series of reactions is 
the fact that iron is removed from the positive electrode to make 
ferrous sulphate and later ferrous hydroxide, and the size and 
weight of this plate are reduced thereby. This loss of metal 
from the buried plate is proportional to the current flowing there- 
from. Now if the track return circuit be of high resistance, a 
portion of the return current will flow back to the power station on 
underground pipes and cable sheaths, leaving these conductors at 
points near the power station to complete the circuit through the 
earth or on the rails and negative cables to the switchboard. 

Since the above chemical reactions take place in the case of 
electric railway currents leaving water and gas mains and the 
sheaths of telephone cables and entering the earth with values 
ranging from an infinitesimal leakage up to several hundred 
amperes in extreme cases, the importance of the study of the mag- 
nitude of troubles from electrolysis and the remedies to be applied 
is at once apparent. 

In the early days of electric traction the bonding of the track 



i8o 



ELECTRIC RAILWAY ENGINEERING. 



and the proper installation of a low-resistance return circuit were 
seriously neglected as has been explained in the previous chapter. 
It was also customary at first to connect the negative terminal 
of the generator with the trolley and the positive to the rail in 




Pipe or Lead Cable 
Fig. 66. — Direction of current with negative trolley. 




EAST 
BOSTON 



Fig. 67. 

many installations, this being just the reverse- of the present 
method. These two conditions tended, first, to force a relatively 
large proportion of the current to follow the pipe and cable sys- 
tems in place of the track and, secondly, to make such pipe and 
cable systems positive to the rail over a wide area of territory in 
the average city. 



ELECTROLYSIS. 



l8l 



This condition is clearly shown in the accompanying Fig. 66, 
which shows the direction of earth currents, and Fig. 67, represent- 
ing the conditions in Boston, Mass. when the question of danger 
from electrolysis was first seriously considered. At the time this 
map was plotted from a large number of tests made of the voltage 
between pipe systems and rails, the trolley was negative and the 
rails positive. The shaded area designated as the " danger area" 
represents the territory in which the pipe systems are positive 
to the rails and therefore in which electrolysis might be expected 
to take place. The large extent of this danger area implies a 
great amount of possible trouble from electrolysis and a consid- 
erable expenditure of time and money for the proper maintenance 
of tests and the location of serious leakages of current. 



t 

+ 



^ 




nnnnn 



B^^"'^©^ 




d: 




Pipe or Lead Cable 
Fig. 68. — Direction of current with positive trolley. 



A marked advance was soon made, however, in this problem 
when the trolley was connected with the positive terminal of the 
generator and the rails with the negative terminal as in Fig. 68. 
This change would naturally limit the danger ^one to a compara- 
tively small area near the power station where the current which 
returned on the various pipe lines would leave these conductors 
and pass through the earth to the rails or return conductors and 
thence to the negative terminal of the generator. The effect of 
such a reversal of trolley polarity is obvious in Fig. 69 which 
represents a potential map of the territory included in Fig. 67 
taken after the trolley of the West End system of Boston was 
made positive. This limitation of the area in which electrolysis 



l82 



ELECTRIC RAILWAY ENGINEERING. 



may take place would usually increase the current leaving the 
pipes at any one place. To prevent serious trouble from elec- 
trolysis at those points it is customary to connect the pipes with 
the rails or return negative feeders by means of heavy copper 
cables. In fact this practice is often employed at other points 
along the line where pipes are found to be positive to the rail. 
This, policy, however, unless carefully carried out, often in- 
cr eases the electrolytic effects from any pipes which happen to 




EAST 
BOSTON 



Fig. 69. 



be left unconnected with the rails because of the greater area 
exposed by negatively connected pipes and therefore the presence 
of lower resistance paths through the earth. Such a condition 
is well illustrated by Fig. 70. 

In this connection it might be of interest to note some of the 
results of electrolysis with currents of different magnitudes. 
Experiments have proved that one ampere flowing steadily from 
an iron surface will remove approximately 20 lb. of iron in one 
year, while the same current flowing continuously from a lead 
cable sheath or pipe will eat away 75 lbs. of lead in the same time. 
A 48 in. iron water main in Boston was pitted in various places 
to a depth of 9/16 in. in from four to five years, the average po- 
tential between pipe and rails being 8 volts with a current 



ELECTROLYSIS. 



183 



flowing in the pipe ranging from 5 to 95 amperes. In this case 
the pipe was about 21/2 ft. below the rails of the street railway 
company. 

Nor is the trouble confined alone to the points where the 
current leaves the pipe for other conductors. The joints in pipe 
lines often have relatively high resistance as compared with the 
pipe itself and even when compared with the surrounding earth 
in some instances. This is particularly true of the so-called bell 
and spigot pipe which is so commonly used for large water mains. 
At these high resistance joints the current or a portion thereof 
passes in a shunt path through the earth around the joint. This 




Water Pipe 
Fig. 70. — Current with portion of pipe system bonded to rail. 



causes an eating away of the iron on one side of the joint only, 
if the current flow is always in one direction. This effect at the 
joint is, of course, increased when the pipes are connected with 
the power station by means of copper conductors for the reason 
that such connection tends to increase the flow of current in the 
pipe line. Because of the increase of electrolysis at the joints and 
the impracticability of bonding these joints, many engineers are 
opposed to this method of decreasing electrolysis. 

Aside from the above mentioned methods of electrolysis 
reduction, two other plans have been proposed, although neither 
has been adopted to any extent. Both of these proposed plans 
involve the use of the double overhead trolley. In one case the 



184 ELECTRIC RAILWAY ENGINEERING. 

second trolley takes the place of the rail return, the rest of the 
system remaining unchanged, while in the other plan the rail 
becomes the neutral of the familiar three-wire system. In the 
latter case a potential of approximately 1200 volts is maintained 
between the two overhead trolley wires while half this voltage is 
impressed between either trolley and the rail. Obviously only the 
current due to unbalanced load on the two sides of the three-wire 
system would return to the power station on the rails and, as this 
would be a very small portion of the total in a well planned sys- 
tem, the trouble from electrolysis would be reduced considerably. 
With the 600 volt two-wire system, however, no connection is 
made between rails and power station and although there may be 
local currents in the rails and earth in some instances, these earth 
currents and the electrolysis resulting therefrom are reduced to a 
minimum. 

The principal objections to these two systems which have 
probably prevented their general introduction may be listed as 
follows : 

High first cost. 

High maintenance cost. 

Difficulties in insulation. 

Complication at crossings. 

Greater overhead obstruction of streets. 
It is believed that the above difficulties are self-explanatory in a 
system of this type, involving as it does the support of two heavy 
bare conductors at a distance of from 15 to 20 ft. above the street, 
separated from each other by a distance of from 12 to 18 in. and 
maintained at a potential difference of either 600 or 1200 volts. 
No further description of such installations will therefore be given. 
Suffice it to say, however, that although the advantages of this 
system from the standpoint of electrolysis prevention were set 
forth in the very infancy of electric traction, there are not more 
than three or four such systems in operation in the United States 
today. Conspicuous among these systems have been the instal- 
lations at Cincinnati, Ohio, and Key West, Florida. 

Some municipalities attempt to insure themselves against trou- 
bles from electrolysis by requiring that the fall of potential on all 
track return circuits be within a certain predetermined limit. For 



ELECTROLYSIS. 



i8s 



example, in rehabilitating the electric railway systems in Chicago 
recently a maximum possible rail drop of 25 volts was specified 
by the city. In order to avoid exceeding this limit with maximum 
traffic, negative return feeders were necessary and as the distribu- 
tion system was largely underground, provision was made for 
these negative cables in the conduit lines. Fig. 71 illustrates 
the standard track construction adopted involving the use of 
frequent cross bonds connected to the longitudinal negative 
return cables. 




rl 



i 



^00,000 



r^l>= 



111 



f 



1,000 CM. Bare Copper CaDle (Min.) 
Fig. 71. — Standard cross section of track construction in Chicago. 

The above regulation is a step in the right direction, for it seeks 
to remove the cause of the trouble, i.e., eliminate stray currents, 
rather than so direct the existing stray currents that they may do 
no harm. If stray currents are to be prevented or at least reduced 
to a minimum, it is necessary to reduce the resistance of the re- 
turn circuit as low as possible. Another method which accom- 
plishes this same end more completely is the use of a negative 
booster connected in series with the return circuit or often con- 
nected to a single point in the return circuit and therefore lower- 
ing the potential of that point to such a negative value that the 
current will not leave the rail. In order to do this it is only neces- 
sary to supply a low voltage heavy current generator driven by a 
motor in the substation with its negative terminal connected to the 
return circuit at the point of greatest leakage. This method may 
be likened to the formation of a vacuum on a pipe line at some 
particular point in order to draw the contents of the pipe system 
to that point because of its low absolute pressure. 

Early in this chapter the statement was made that the question 
of electrolysis has been given decreasing publicity by the water and 
gas companies since the difficulties in connection therewith were 
first made manifest in the early nineties. This has taken place in 



1 86 ELECTRIC RAILWAY ENGINEERING. 

spite of the fact that no complete cure has been found for the 
difficulty. This apparently paradoxical condition has come 
about largely because of the increased activity on the part of the 
railway managements to better inspect and maintain the track. 
The value of a low resistance return circuit is now well known 
among electric railway men and by frequent testing, by replacing 
and increasing the capacity and efficiency of bonds, and by the 
installation of cross bonds and negative return conductors, the 
track circuit has been placed in a condition to return practically 
all the current to the power station so that the leakage by way of 
shunt paths through the earth and its pipe systems has been 
reduced to a minimum. 

In testing for electrolysis troubles, methods similar to those 
outlined in the previous chapter are adopted. As dangerous 
electrolysis occurs only at points where the pipes are positive to 
the rails, such points are readily determined by connecting a 
milli-voltmeter between the rails and convenient points, such as 
hydrants on the pipe lines. The positive pipes are then perma- 
nently connected to the rails by means of a copper bond. To 
determine the actual current flowing in the pipes it is only neces- 
sary to find the fall in potential between two convenient points 
on the pipes at a known distance apart. The resistance of the 
pipe can usually be found from tables or it may be found by test. 
The current is then calculated from Ohm's law. That such 
leakage currents are produced by the railway system and that 
they vary with the load on the railway system is well demonstrated 
by the tests plotted in Fig. 72 which represent readings of current 
flowing in a 36-in. water main compared with the power station 
log of current output during the same period of time. The 
similarity of the two curves plotted with the same abscissae of time 
is rather surprising. 

In the case of electrolysis, therefore, as well as in many other 
difficulties which engineers encounter from time to time, it may be 
said that at the time the effects of this action were first discovered 
in Boston the problem looked most serious for electric railways 
throughout the country and many suits were brought by water, 
gas, and telephone companies against the railway companies for 
damage to pipe lines, etc., the test case at Peoria, Illinois, which 



ELECTROLYSIS. 



187 



railway men have been following most closely, being still unde- 
cided after years of controversy. The problem has been studied 
carefully, however, and such means of reducing its serious effects 

^ A *5 O 

S^ <» a> 




Fig. 72. 

devised that while it can never be entirely eliminated, it may be 
said that its results are no longer serious, if careful and persistent 
testing and bonding be the policy of the railway company. 



CHAPTER VIII. 
Signal and Dispatching Systems. 

The problem of dispatching cars and of protecting one car 
from another on the same section of track is largely confined to 
interurban systems, for in the case of city railways, speeds are 
low, the headway is small, and double tracks are commonly in use. 
Cars are therefore usually operated as closely as possible on a 
predetermined schedule by the car crews and considerable respon- 
sibility is placed upon them for the regaining of schedule time in 
case of delay. In many cities branch line dispatching is done 
by a starter stationed in the city square or at the junction point 
of branch line and the main tracks . For the above reasons, there- 
fore, this chapter will be principally devoted to interurban systems, 
although the possible application of a number of the signal systems 
to urban car operation will be obvious. 

A complete system of train dispatching by a single dispatcher 
for the entire road does away to a large extent with the necessity 
of signals other than those under the control of the dispatcher 
installed for the purpose of attracting the attention of a train 
crew for special orders while enroute, or to stop a car in case of an 
error in orders discovered after the last communication with the 
crew. Most of the signal systems are therefore operated in 
conjunction with a dispatching system and act as a check there- 
upon. Some of the more complete systems, however, are operated 
with little attention from the dispatcher and the complete auto- 
matic block signal system on a double track road may be practi- 
cally independent of dispatcher's orders. 

Where a dispatching system is adopted, those signals commonly 
used in steam railroad practice are occasionally found on electric 
lines, involving the manually operated signals and telegraphic 
train orders to way station agents. Even the "staff" system 
which is used extensively in England may occasionally be found. 
This is really a combined signal and dispatching system consisting 

i88 



SIGNAL AND DISPATCHING SYSTEMS. 1 89 

of two electrically interconnected mechanisms, one at either end 
of a block, which permit a staff to be removed therefrom if there 
be no train in the block ahead. A second staff cannot be removed 
from either of the terminal stations until the missing staff has 
been replaced at the farther end of the line. This system not 
only protects the block but also gives the train crew tangible 
evidence that they have the right of way in the block. 

The dispatching system most common to electric railways is 
that using the telephone for communication between dispatcher 
and train crew. Telephone booths are either provided at sidings 
or a portable telephone is carried on each car which may be 
readily connected with the telephone circuit paralleling the track 
by means of a flexible cable and two-pole plug switch. It is cus- 
tomary to require the motorman to receive the orders and write 
same on an order blank which furnishes a carbon copy for the 
conductor. The order is checked by the conductor reading from 
the carbon copy to the dispatcher over the telephone. This 
check message is either ok'd or corrected by the dispatcher. 
Whereas there are many modifications of this method in use, 
the telephone is very generally adopted and has proved very 
satisfactory. In fact several of the steam railroad trunk lines 
have adopted the telephone in place of the telegraph for train 
dispatching. 

Such telephone lines should be constructed for dispatching only, 
the business to be transacted between other officials or depart- 
ments of the road being provided for by another line. This 
duplicate line is fully warranted in the interests of safety and the 
avoidance of train delays. Care should be taken also to insist 
upon the repeating of orders, for serious wrecks have occurred 
due to the train crew receiving but a portion of the order or mis- 
taking an order given to a crew at the dispatcher's office with the 
receiver off the hook for an order intended for them. Repeating 
an order will correct these errors. 

Aside from the telephone order and the possible stop signals, 
mentioned above, which may be under the control of the dis- 
patcher, some railway companies provide a means at the disposal 
of the dispatcher for shutting off power from any desired section 
of trolley in order to prevent a wreck in case of emergency. Still 



190 ELECTRIC RAILWAY ENGINEERING. 

Other officials believe this to be a dangerous tool in the hands of 
the dispatcher upon which he may tend to rely too frequently. 
Such a device applied to the feeder circuit breakers on the power 
station switchboard is illustrated in Fig. 73. In this case the 
tripping device is operated by a relay which is supplied with 
current from the trolley with a number of incandescent lamps in 
series and with the controlling switch in the dispatcher's office. 
This particular device is used by the Indianapolis and Louisville 
Traction Company. In making use of this device it should be 
remembered that it does not necessarily enable the car to be 




Fig. 73. 

stopped at once, for in the case of high-speed interurban roads the 
cars may travel for considerable distances at high speeds without 
the use of power. When the lighting circuit is not in use there is 
no indication to the car crew that the power has been shut off. 

Signal Systems. — Returning to the signal systems which 
usually augment but may replace the dispatching system, it may 
be said that the present systems have been a gradual growth from 
the single incandescent five lamp series circuit between trolley 
and ground to the more elaborate automatic block signals similar 
to those used on steam roads which are now being rapidly adopted 
by the large interurban railroads. 



SIGNAL AND DISPATCHING SYSTEMS. 



191 



For protection against accidents and in order that the schedule 
may be maintained, it is desirable that the train crew should 
know upon entering a block or certain section of the road 

1. Whether there is another car in the block. 

2. How many cars there are in the block. 

3. What direction the cars are going. 

The latter requirement is, of course, applicable to single track 
roads only. As a matter of fact, nearly all signals are confined 
to the first case only or the first and third classes, but very few in 

Trolley 



11 

-C— 0-1 



AV 



VI 



G^F 




Fig. 74. — Simple lamp signal. 



general use answer the second question. In order to do this 
automatically the circuits have become too complex, involving 
difficulties and excessive expense in their maintenance. Signals 
displayed on the cars are used to signify that another car is follow- 
ing in the same block. 

Probably the most simple arrangement used as a signal, and one 
to which several roads have returned after trying out the more 
nearly automatic types, is that shown in Fig. 74. This consists 
of a series of five incandescent lamps connected as shown by means 
of a double-throw switch between trolley and ground, two of each 
group being located at one end of the block and three at the other. 
The group of three lamps is placed behind a white or green lens 
and the two lamp group provided with a red lens. Upon enter 
ing the block the circuit is closed by means of the switch which 
lights a red light at the opposite end and a white or green light at 
the entering end. Upon arrival at the other end of the block the 
lights may be switched out and the circuits are such that the lights 



192 



ELECTRIC RAILWAY ENGINEERING. 



may then be lighted from either end. An extra circuit duplicating 
that of Fig. 74 should be provided, however, for operation in both 
directions. The advantages of this signal are its simplicity and 
the necessity of one of the crew leaving the car, when stopped, to 
operate the signal switch. Its disadvantages are that the signal 
light may be extinguished and the signal reversed from either end 
with a car still in the block and if the switch be accidentally left 
in the off position the signal cannot be operated from the other end. 
Elaborating upon this principle and adding the automatic 
feature, the United States Signal Company has developed a signal 



Trolley 





a 



Fig. 75. — United States signal. 



for single track blocks which has been adopted by many roads. 
It operates from the trolley circuit and consists of one signal box 
and trolley switch at either end of the block connected as in Fig. 
75 and requiring two wires throughout the length of the block. A 
car entering the block at (A) makes a momentary connection be- 
tween the trolley wire and wire No. 4, as the trolley wheel operates 
the iron tongue switch mounted on the trolley wire. This momen- 
tary connection closing a circuit to ground through a relay and a 
suitable resistance, completes the permanent circuit connecting 
the trolley wire through No. i, the green lamp at (A), the signal 
line wire, the red lamp at (B), through resistance in box (B) to 
ground. Other cars entering at (A) do not change the signal set- 
ting, but a car leaving the block at (B) energizes wire No. 5 through 
the agency of the overhead trolley switch and trips the relay which 



SIGNAL AND DISPATCHING SYSTEMS. 1 93 

extinguishes the red light. A car entering at (B) performs the 
reverse operation, lighting the green light at (B) and the red signal 
at (A). The boxes and switches are therefore interchangeable. 
Red and green disks are displayed in some types of this signal for 
day use, although the lights are commonly used as day signals as 
well. This type of signal has given a fair degree of satisfaction 
although its maintenance expense is high, especially because of 
damage by lightning. In fact it is very difficult to design a signal 
operating upon a grounded circuit which will not be seriously 
affected by lightning. The widely varying voltages on the various 
sections of the average interurban line also introduce difficulties 
in the design of signals to be operated from the trolley circuit. 
It should be noted that in both of the above systems the motor- 
man is assured that the red signal has been displayed at the farther 
end of the block if the green light appears at the entering end. 
This fact is seldom determined by the steam railroad engineer 
who relies upon the automatic block signal to give the danger indi- 
cation without actually observing the signal movement himself. 

A signal system very similar to the above is manufactured by 
the Nachod Signal Company. In addition to the above protec- 
tion, however; this signal counts the cars into the block as they 
enter and does not return to "clear" until each car has been 
counted out. An indication is given the motorman by means of 
the flash of a lamp that his car has been registered as the trolley 
switch is passed although the signal aspect remains unchanged. 
A further protection is offered in this system in that the signal 
may be made an "absolute block" system by manually opening 
one of the line wires by means of a pole switch, thus causing red 
signals to be displayed at both ends. This provision is of conve- 
nience when a line repair crew is working in the block. 

Still another type of signal similar to the above displays an 
orange-colored light when no car is in the block and a green 
cautionary light as the car enters in series with the red danger 
signal at the distant end. The principal difference in the opera- 
tion of this signal is that it makes use of a single rail with each 
block insulated from its neighbor as far as the flow of signal cur- 
rent is concerned, as will be explained later in connection with 
single rail automatic block signals. 
13 



194 ELECTRIC RAILWAY ENGINEERING.' 

Automatic Block Signals. — The signals described thus far 
have been installed on sections of single track between sidings to 
control and protect cars operating in both directions. In distinct 
contrast to these is the automatic block signal used to protect cars 
on sections of double track from the danger of operation with too 
small headway and yet to permit the minimum safe headway to 
be maintained under conditions of heavy traffic. This is the 
type of signal used to an ever increasing extent on steam trunk 
lines, although the details of design vary somewhat when applied 
to electric service. While the large interurban systems of the 
Middle West are just beginning to consider seriously the question 
of equipping their lines with automatic block signals, this type 
of signal has for a long time found a most important application 
in elevated and subway installations in the largest cities of the 
country. A rather detailed study of this type of signals, therefore, 
is very appropriate at this time. 

A "block" as the term is used in this discussion, may be 
defined as a section of track so protected that but one train can be 
in that section at any given time, no other train being allowed to 
enter until the last truck of the previous train has left the section. 
The length of these protected blocks will be determined in each 
particular case. They must be sufficiently long to enable a 
heavy high-speed train to stop within their limits and yet suffi- 
ciently short to permit the smallest safe headway between trains 
during rush hours. They usually vary from 2000 ft. to 2 miles 
in length. 

At the entrance to each block a signal must indicate, both by 
day and night, whether or not there is a train in the first block 
beyond. Such a signal is termed the "home" signal. In addi- 
tion it has been found advisable, if high speed trains are to operate 
smoothly without frequent periods of slow-down, to install an 
additional signal, usually upon the same standard as the home 
signal, to indicate the condition of the second block ahead. This 
signal is termed the "distant" signal. 

These indications are usually given in daylight by means of a 
semaphore and with colored lights at night. As considerable 
trouble has been experienced from the use of colored "bulls- 
eyes" or signal "roundels" at night upon roads using the very 



SIGNAL AND DISPATCHING SYSTEMS. I95 

powerful headlights owing to reflections from unlighted roundels 
appearing as signals, it is believed that if the more powerful 
headlight is adopted the semaphore or "position" signal will be 
ultimately very generally used as a night signal as well, being 
sufficiently well illuminated by means of the headlight to permit 
the accurate reading of signal aspects/ The semaphore 
when in a horizontal position indicates "danger," while the 
"proceed," or "clear" signal is usually indicated by a 60° angle 
in the lower quadrant. In some types of signals three angular 
positions are used, a 45° position indicating "caution" and a 
vertical position "proceed" or "clear" aside form the "danger" 
indication. In a few instances, and upon the Pennsylvania 
railroad in particular, the "clear" position is represented with 
the semaphore in the upper quadrant, the arm falling to the hori- 
zontal position by gravity to indicate "danger" or when anything 
is wrong with the signal apparatus. Such a signal is designated 
as a "normal danger" signal as contrasted with the "normal 
clear" types described above. Each has its rather obvious ad- 
vantages and disadvantages and therefore its ardent supporters 
among signal engineers. The corresponding signals at night are 
usually red for "danger," green for "clear" and yellow for 
"caution," although the two latter colors vary somewhat for the 
different roads. 

As the train arrives at the entrance of a block the home signal 
denotes the condition of the first block and the distant signal that 
of the second block ahead. With both at "danger" the two 
blocks ahead are occupied and the train stops. With the home 
signal at "clear" and the distant signal at "danger," the first 
block is clear and the second occupied. The train may enter the 
block under control. With both signals at "clear" the engineer 
knows that two blocks ahead at least are clear and he may enter 
the block at full speed. The distant signal at the first block and 
the home signal of the second block are so interlocked that the 
former cannot move to "clear" until the latter has attained a 
similar position. Upon entering the first block under control 
with the distant signal at "danger" it is expected that the next 

^ "Headlight tests" by Professors C. F. Harding and A. N. Topping, A. I. E. E., 
Vol. XXIX. 



196 ELECTRIC RAILWAY ENGINEERING. 

home signal will be at *' danger." Since, however, the signal 
may have changed before the train reaches the second block, it is 
often advisable to install a second distant signal within safe stop- 
ping distance of the second block. This is especially true if the 
second block signal is not readily seen at some distance, since it 
avoids slowing down if the second block has been cleared in the 
meantime. 

While it is unnecessary to describe in detail the operating 
mechanism of the semaphore and colored roundels in its various 
forms, it may be said that this movement is accomplished by 
means of mechanical levers and bell cranks, gas or air pressure 
operating pistons in cylinders located in the base of the signal, or 
by electricity used through the agency of a solenoid or series 
motor. The control of the local apparatus at the signal by means 
of electric relay circuits is, however, of greatest importance and 
will be explained in detail. 

Steam Railroad Practice. — As the block signal systems used 
with electric roads have been patterned after the more simple 
steam railroad installations a description of the latter will aid in 
understanding the former. The two rails for a block in length 
are insulated from one another and also from the adjacent rails 
of neighboring blocks by means of insulating rail joints. The 
various rail lengths of a single block are bonded together in a 
manner similar to that described in Chapter VI, but with much 
smaller wire bonds. A gravity or storage battery of i or 2 volts 
e. m. f., located in a manhole below the frost line, is connected 
between the rails at one end of the block. At the other end of 
the block a sensitive relay is connected across the two rails. This 
relay is usually mounted in the base of the signal tower and 
thereby protected from the weather. Where there is no train in 
the block the battery supplies current to the relay by way of the 
two rails and the signal is held in the "clear" position. As the 
first trucks of a train enter the block, however, the wheels and 
axles short-circuit the relay and it opens, closing the local circuit 
which throws the semaphore and colored roundels into the "dan- 
ger" aspect. The signal is locked in this position until the 
movement of the last truck of the departing train from the block 
removes the short circuit, closes the relay, and clears the signal. 



SIGNAL AND DISPATCHING SYSTEMS. 



197 



Such is the very simple circuit and mechanism of the automatic 
block signal for steam railroads and although its first cost has 
been sufficiently high to render its adoption rather slow, its main- 
tenance is not excessive and its positive operation is to be depended 
upon. In fact in one instance but one failure to operate in 
250,000 was the record of operation on a large signal system 
during the period of one year. 

Electric Railroad Block Signals. — With the electric railroad, 
which makes use of the track rails for the return of heavy currents 
to the substation or power house, the problem becomes a more 
difficult one, as the rails are no longer free for sectional insulation 



Trolley or Third Rail 



n^ffii 



D.C. Kail way 
Generator 
Return Rail 4, — 



D- 



I 

Signal 



Signal Light 



u 



n 



Block Rail 




S5 



NAAAA/| 



Fuse- 

Non.-inductive. 
Resistance 

Reactance Coil 

Track _> 
Transformer 

*-A.C. Track 
-J Relay 



^ 



Rail Insulation 



^\X I Signal A.C. 



A.C Signal Mains 



^^^ 



Generator 



t 



Fig. 76. — Single rail alternating current block signal. 

as in the case of steam roads. One method of overcoming this 
difficulty which would naturally suggest itself is to use one rail 
for signal purposes and the second rail for the return of power 
current. The further use of alternating current for the signal 
relay would permit selective operation of the latter without inter- 
ference from the power current. Such a system is successfully 
used in the New York subway, its principle of operation being 
illustrated by Fig. 76. 

By referring to the above figure it will be seen that one rail 
termed the "block rail" is insulated in sections, one block in 
length, constituting a circuit for signal current only. The other 
rail carries the current from the trains and also acts as a common 
return circuit for the signal system. Alternating current for the 
signal circuit and also for the signal lamps is supplied through 



198 



ELECTRIC RAILWAY ENGINEERING. 



transformers from single-phase alternating current mains paral- 
leling the track. If the power current is flowing in the return 
rail from left to right the voltage between rails at (B) will be 
slightly less than at (A) due to the fall of potential in the rail. 
This will cause some of the direct current to pass through the 
relay connected between the rails at (A), thence through the 
block rail and the transformer secondary to the return rail at (B), 
the latter forming a high resistance shunt path to the length of 
return rail (AB). In order to limit the amount of this current 
which would otherwise produce a uni-directional magnetic field 




Fig. 77. 

in the relay and transformer, high noninductive resistances are 
inserted in series with the relay and transformer secondary and 
a reactance coil shunted across the relay. While the direct 
power current following the block rail will pass freely through this 
reactance, the signal alternating current will be prevented by the 
impedance of the reactance coil from taking that path and will 
therefore pass through the relay. As an additional precaution 
in the case of the transformer an air-gap is introduced into the 
magnetic circuit to reduce to a minimum any magnetic flux 
which might be produced by the relatively small leakage direct 
current. 



SIGNAL AND DISPATCHING SYSTEMS. 1 99 

With these added precautions the relay system operates exactly 
as in the case of steam railroad equipments with the exception 
that the relay must be of the alternating current type. A relay 
depending upon the torque produced by eddy currents induced 
in an aluminum disc being acted, upon by the magnetic field set 
up by the current in the relay has been adopted for this purpose. 

In the case of the particular installation of this system in the 
New York subway, the alternating current distribution is at 
500 volts and 60 cycles, the track transformers stepping the po- 
tential down to 10 volts, while the signal lamps are operated at 
55 volts. The resistance of the track and signal circuit is such 
as to impress approximately five volts upon the relay. The power 
factor of the circuit is in the neighborhood of 80 per cent, and 
the power taken by an average block but 80 watts. A typical 
installation is represented in Fig. 77. 

Block Signals for Alternating Current Roads. — When the 
problem arose to equip electric roads operating with alternating 
current in the track rails, it may be readily seen that still further 
difficulties were encountered. The problem was fairly well 
solved, however, by the development of the two rail signal system 
making use of inductive bonds, although this equipment can 
hardly be considered in a state of perfection as yet. It has been 
adopted as well in some instances on direct current roads where 
the full conductivity of the two rails was considered of sufficient 
value to overcome the slight disadvantages of a system requiring 
the use of inductive bonds. 

The principle of this type of signal system, similar to that 
operating on the single-phase terminal electrification of the 
New York, New Haven and Hartford Railroad in New York, 
is illustrated in Fig. 78. It will be seen that each rail is insulated 
at the ends of the block as in the case of steam railroad practice, 
but inductive bonds are installed between the rails at (AB) and 
(EF) of sufficient capacity to carry the train current. The 
middle points of adjacent bonds are connected together so that 
there is a complete electrical circuit from train to power house by 
way of each rail, this circuit involving one-half of each bond at 
every block. These bonds are carefully designed so that their 
counter e. m. f. will not be great at the frequency of 25 cycles or 



200 



ELECTRIC RAILWAY ENGINEERING. 



below, at which the train motors operate, but will be sufficiently 
great to produce a useful difference of potential between the rails 
in the signal circuit which is operated at 60 cycles. In other 
words a very interesting application is made of the theory that 
the reactance of a coil is proportional to the frequency and the 
bonds are therefore designed to operate upon one frequency only. 
The immediate source of power is the transformer as in the 
single rail system, but in this case the power current is sufficiently 
well balanced in the two rails to prevent unbalanced currents 
flowing in the transformer and the air gap in the magnetic circuit 

Trolley 



BaiVInsulatioa 

" — y r: 




D.C. Railway:, 
Generator 



lL Inductive Track Tl^ 



Relay 



A.C. Signal Mains^ 




B -( F 
Inductive 
/vv^\ Bonds 

Track 
Transformer 



A.C. Signal 
Generator 

Fig. 78. — Double rail alternating current block signal using inductive bonds. 

is therefore omitted. The transformer is designed with a rela- 
tively high leakage factor, however, in order that the current"may 
not be excessive when the secondary of the transformer is short 
circuited by the train in the block. It will be noted further that 
for the above reasons the auxiliary resistances and reactance 
shunt across the relay may be omitted. 

With these changes and a slight change in the design of the 
relay, the system operates as in the single rail design. The 
direction of the power current is shown by full lines and that of 
the signal current by dotted lines in Fig. 78. 

In all of the above automatic block systems it should be noted 
that if the track relay circuit be opened the action is the same as 
though the relay were short circuited by a train in the block, i.e., 
the signal is thrown to "danger." This action has proved of 
great value in detecting broken rails and has probably prevented 
a number of wrecks thereby. 



SIGNAL AND DISPATCHING SYSTEMS. 20I 

In a few instances this type of signal has been used on single 
track blocks, but here the difficulty lies in not being able to tell 
which way the train is moving that is occupying the block, while 
in the double track system, if the block were not cleared in the 
usual time, the train might move forward slowly in order to locate 
the trouble, with the knowledge that the train ahead was headed 
in the same direction. In the case of the single track, however, 
it would be necessary to send a flag-man ahead to prevent a 
head-on collision if such an investigation were attempted. It is 
probably for this reason, together with the larger percentage cost 
of block signals, that they have not been widely installed on single 
track roads. Upon the Harriman lines, however, where they 
have been used to a considerable extent on single track it is claimed 
that their detection of broken rails as above explained has well 
warranted their installation. 

Cost. — The Electric Journal is authority for the statement that 
the average cost of an automatic block signal system, with com- 
bined home and distant signals on a single standard will vary 
from S750 to $1100 per block, depending upon the length of 
block, number of switches, and method of signal control. An 
average value for maintenance has been placed at from $75 to 
$100 per annum for a two-arm signal. 

It may have been inferred from the previous discussion that 
there is a wide variety of signal systems with widely varying de- 
grees of protection and corresponding first costs, from which to 
choose. While a theoretically perfect system has not yet been 
developed, it is safe to say that the more complete systems have 
not been cast aside by the interurban railroads because of their 
unsatisfactory design and operating qualities, but rather because 
of their high first cost and maintenance charges. As the com- 
bined result of some rather serious wrecks which have recently 
taken place on interurban roads, the advertising value of a com- 
plete automatic block signal system and the increasing pressure 
which is being brought to bear by state railroad commissions 
throughout the country, it is believed that the automatic block 
signal will be pretty generally adopted in the near future and the 
resulting developments in the electric signal field correspondingly 
rapid. 



PART III. 

EQUIPMENT 



CHAPTER I. 
Track Layout and Construction. 

The electrical engineer of a proposed electric interurban rail- 
way is often called upon to determine the right of way and super- 
intend the track survey and construction, although in the large 
city systems or extensive interurban developments a technically 
trained civil engineer is usually given this responsibility. In 
either case the electrical engineer should be familiar with such 
general features of the problem as may be herein outlined. 

Right-of-way. — After several proposed routes have been 
suggested for the new railway, possibly with the aid of rough 
preliminary surveys for each, and detailed notes taken of the 
advantages and disadvantages of each, involving the typography 
of the country, number of intermediate towns and amount of 
tributary population served, possible schedules, etc., it is neces- 
sary to decide upon one route. This is usually determined by 
the officials of the company in conference with the engineer. 
With this decision in mind the problem of obtaining the right-of- 
way presents itself and it is often policy not to make the above 
decision public until after the greater portion of the right-of-way 
has been secured. In fact it has sometimes been found advisable 
to propose publicly two possible routes and even go to the 
extent of purchasing options on land along each in order that an 
element of competition may enter, preventing land and options 
from assuming exhorbitant values along the desired route. 

Great diplomacy must be exercised by the advance real estate 
agent in order to secure the desired route at a reasonable figure 
and without too many concessions, which often complicate the 
schedules and embarrass the company when operation begins. 
It must always be remembered that much of the future traffic will 
come from those with whom these preliminary negotiations are 
made. 

If satisfactory locations cannot be secured, either because of 

20^ 



2o6 ELECTRIC RAILWAY ENGINEERING. 

opposition to the proposed road or too high prices being placed 
upon the land, right of eminent domain may be secured through 
the court and certain sections of the route condemned and thereby 
purchased at a value appraised by the court or a commission 
appointed by the court. As this proceeding makes public the 
proposed route and prejudices some against the company, it 
should be avoided if possible, but if found necessary, it should be 
postponed until the remainder of the land has been secured. 

It will be noted that the above discussion presupposes a private 
right-of-way for the road. Such a route is generally much to be 
preferred except within the limits of intermediate towns, and even 
in the latter case a route but a few blocks from the center of town 
on a back street with little traffic, where speeds may be fairly 
high and frequent curves avoided, should be given serious con- 
sideration. In some instances interurban railroads run for miles 
along country roads, but it is usually done at the expense of low 
schedule speeds, and high maintenance charges due to restric- 
tions often imposed by town boards and street commissioners, not 
to mention frequent and serious accidents. A slightly larger first 
cost for a private right-of-way is justified in most cases from the 
standpoints of schedule, safety and independence from ordi- 
nances stipulated by outsiders not only, but from the purely finan- 
cial consideration as well. 

A right-of-way at least loo ft. in width should be secured to 
allow for possible double track with necessary cuts and embank- 
ments provided with adequate drainage ditches. Such a strip 
of land averages twelve acres to the mile. 

With the route approximately determined and the right-of- 
way secured, a final survey should be made to locate the exact 
line for the track and to determine the profile. With the exact 
profile plotted the grade line may be drawn consisting of an 
average line through the profile representing a series of grades, 
with none exceeding 2 per cent, if possible, and with as close a 
balance between ''cuts" and "fills" as may be secured in order 
that the haul for excavation and embankment may be a mini- 
mum. While grades as high as 7 or 8 per cent, sometimes 
exist on interurban roads it will often be found that when the 
first cost of the extra heavy car equipment and possibly the 



TRACK LAYOUT AND CONSTRUCTION. 



207 



Station equipment necessary to climb these grades, together with 
the annual cost of extra power required are balanced against the 
fixed charges on the extra cost of reducing the grade by means 
of a deeper cut or a slight change of route, the latter policy would 
have been the better of the two. 

Before accurate estimates can be made or contracts let for 
preparing the sub-grade it will be necessary to learn something 
more of the character of the sub-soil. It will be assumed that 
the general nature of the country and its geological formation were 
carefully noted during the preliminary survey, since the decision 
of the proper route depends largely upon such a study, especially 
when a river is to be paralleled and possibly bridged occasionally. 
It is now necessary, however, to have test borings made as deep as 
the deepest proposed cut at intervals along the line sufficiently 
frequent to obtain a good idea of the type of excavation to be 




Barrow Pit 







Uuless otherwise 
ordered 



'■1 



\<^^<<i^ Unless otherwise 
ordered 



EMBANKMENT 



Fig. 79. 



expected and the necessity of driving piles or installing mattress 
concrete or timber in case of possible quick sand. A contract can 
usually be placed for such borings with their results either repre- 
sented to scale on a drawing for each station or better by a 
glass tube filled to scale with the various strata of sub-soil found. 
With this information at hand a series of cross sections at right 
angles with the base line at stations 100 or 200 ft. apart, or possibly 
less where the profile is very irregular, may be made and the 
volume of excavation and embankment calculated. A list of cut 



2o8 ELECTRIC RAILWAY ENGINEERING. 

and fill expressed in cubic yards of each type of sub-soil from 
solid ledge to soft clay may then be made for each mile of road 
and estimates readily calculated and contracts signed. Typical 
sections of cuts and embankments will be found in Fig. 79, while 
estimates of their respective costs in the South will be found at the 
end of the chapter. These latter values vary greatly with local 
conditions and are usually based upon a certain maximum length 
of haul between a cut and the corresponding fill into which the 
excavated material may be deposited. 

Ballast. — It is safe to say that the experience of interurban 
roads which have been operating for some time demonstrates the 
fact that money expended in first class sub-grade construction and 
rock ballast proves to be the most economical in reducing main- 
tenance charges and providing a smooth riding roadbed which 
does not quickly wear out both itself and the rolling stock. 

The ballast, which is that portion of the roadbed upon which the 
ties are placed, should be sufficiently porous to permit the water 
to run off freely. The best ballast is recognized to be crushed 
rock capable of passing through a i 1/2 in. ring. Coarse gravel, 
however, makes a very good substitute and is very often used 
because of its lower cost. Fortunate indeed is the road that 
secures with its right-of-way one or more borrow pits containing 
good ballast gravel. This ballast is laid for a depth of 6 to 18 in. 
under the ties and should cover the ties to the base of the rail. 

Ties. — Now that the scarcity of good lumber is beginning to be 
felt, with a corresponding increase in first cost, the selection of 
suitable ties and their treatment to insure long life is becoming 
a serious problem. Pine, cedar, white oak, red oak, fir and chest- 
nut are the woods in most common use. The choice between these 
depends largely upon the variety which is native in the locality 
in which the road is being built. Cedar is probably as long lived 
as any, while the ability of white oak to hold spikes is probably 
greater than any other wood. While this variety of tie is gener- 
ally too expensive to use throughout, it is often specified for 
curves where the strain on spikes is of course greatest. 

Herrick gives in the following table an approximate length of 
life for the different varieties of ties as determined by Mr. Hough^ 

^ "Practical Electric Railway Handbook," by A. B. Herrick. 



TRACK LAYOUT AND CONSTRUCTION. 209 

TABLE XVIII. 

Life of Ties. 

White oak 7.4 years. 

Red oak 5.0 years. 

Chestnut 7.1 years. 

Southern pine 6.5 years. 

White pine 6.5 years. 

Red cedar 11. 8 years. 

It is generally considered advisable to specify preservative 
treatment for ties in order to increase their life, although it is 
difficult to determine from experience thus far just how much 
the life is extended thereby. Probably a fair average price for 
an untreated tie throughout the country is 70 cents with a possible 
15 cents per tie increase for treatment. Ties which have been 
embedded in concrete in city construction have shown particularly 
long life, averaging from 10 to 20 years with many rail replace- 
ments. The replacement of rails and removal and replacement 
of spikes during realignment often shorten the life of a tie when it 
has not decayed. Screw spikes have been proposed to obviate 
this difficulty, but they are little used at present because of their 
higher first cost and the greater time required for installation and 
removal. 

Reinforced concrete and steel ties have been experimented 
with, especially abroad. Whereas concrete and steel substruc- 
tures are replacing ties to a large degree in city streets the wooden 
tie for interurban or steam railroad use has not been replaced to 
any extent in this country. 

The dimensions of ties for interurban use are similar to those 
for steam roads, averaging 6'^XS>''X8^, although 5-in. ties may be 
found occasionally. In third rail construction a longer tie is 
installed every 10 ft. to act as a support for the third rail insulator. 
The spacing of ties will be found to vary from 15 to 30 in., but 
an average dimension may be taken as 2 ft. Ties which lie 
under the rail joints are placed nearer together, but their exact 
spacing is dependent upon whether a suspended or supported 
rail joint is used, as will be described later. 

One consideration in connection with the selection of ties which 
has received very little attention is the effect of preservative 
treatment upon their resistance. This is of particular value 
14 



2IO 



ELECTRIC RAILWAY ENGINEERING. 



only where the automatic block signals are installed. From the 
discussion of the previous chapter it will be seen that if the resist- 
ance of the ties be greatly reduced they will act as a shunt to the 
relay and possibly interfere with its proper operation. Tests 
recently made at Purdue University^ upon the resistance of ties 
recorded in the report of the wood preservation committee of the 
American Railway and Maintenance of Way Association prove 




Fig. 8o. 



that ties follow the laws of insulators in general, but that when 
treated with the chloride of zinc preservative process their apparent 
resistance is lowered. Calculated results based upon the data of 
these tests, assuming wet treated ties in wet ballast, show values 
of resistance sufficiently high to prevent serious interference with 
signals. Cases in practical operation have been reported, how- 
ever, in which such interference has been present. 

Rails. — In the selection of rails also, steam railroad practice 
has been followed to a great extent, although the weight of rail 
used is, on the average, less with the interurban roads. This is 

^ Graduate Thesis, Purdue University, by J. T. Butterfield, 19 lo. 



TRACK LAYOUT AND CONSTRUCTION. 



211 



possible because of the lighter weight of trains and the absence of 
reciprocating motion. The interurban roads make use of the 
''T" rail almost exclusively, averaging in weight from 70 to 80 
lbs. per yard. The section which has been very generally adopted 
is the standard established by the American Society of Civil 
Engineers as shown in Fig. 80. In city streets a wide variety of 
rail sections will be found from the "T" rail to the various shapes 
and sizes of grooved girder rails. The "T" rail has been rather 




Fig. 81. 



generally objected to by city authorities because of the danger 
to vehicular traffic offered by the projecting head of the rail and 
the difficulty in paving close to the rail with standard paving 
blocks. Two sizes of girder rails 7 in. and 9 in. in height respec- 
tively have come into general use, the latter being preferred from 
the standpoint of ease in paving. At the 19 10 annual convention 
of the American Electric Railway Association the 9 in. standard 
girder rail illustrated in Fig. 81 proposed by the Committee on 
Way Matters was adopted as well as a similar 7 in. section. These 
are designed for installation in city streets where the traffic is 
particularly heavy. 

The proper chemical composition of rails has been a ques- 



212 



ELECTRIC RAILWAY ENGINEERING. 



tion under discussion for some years, attempts being made to 
obtain a hard rail which shall not be so brittle as to break readily. 
Low conductivity is also a desirable, although not a governing 
feature. The analysis which has been standardized by the 
American Electric Railway Association is given in the following 
table : 

TABLE XIX. 
Standard Analysis for Steel R.\ils. 



Lower 
limit. 



Desired 
composition. 



Upper 
limit. 



Carbon 

Manganese 

Silicon (not to exceed) 

Phosphorous (not to exceed). 



0.6% 
0.6% 



0.68% 
0.80% 



0.75% 
0.90% 
0.20% 
0.04% 



The above table applies to open-hearth steel, as the majority 
of rails are now being manufactured by the open-hearth process. 

The composition of the third or conducting rail may be such 
as to result in a much softer and lower resistance rail. Arm- 
strong gives the following analysis for such rails. 

TABLE XX. 

^Analysis for Third Rails. 

Carbon not to exceed 0.12 per cent. 

Manganese not to exceed o .40 per cent. 

Sulphur not to exceed o 05 per cent. 

Phosphorous not to exceed o . 10 per cent. 

The use of manganese steel for the centers of special work and 
even for complete frogs, switches and curves has been recently 
given a great deal of attention because of its long life. While it 
seems to be the consensus of opinion among railway operators 
that the latter uses of manganese steel are only advisable 
in extreme cases of heavy wear, the adoption of replacable frog 
and switch points of this material is very heartily sanctioned. 

The method of laying rails in city streets departs greatly from 

^ Electric Traction by A. H. Armstrong. 



TRACK LAYOUT AND CONSTRUCTION. 213 

interurban practice, a liberal use of concrete, steel and sand in 
the sub-grade being common practice. Rails are often tempo- 
rarily supported upon wooden ties spaced 5 ft. or more apart in 
order to hold them to gauge while concrete longitudinal stringers 
are being installed for the final rail support. Iron chairs embed- 
ded in the concrete serve to grip the rail flanges after the concrete 
is set. Less elaborate installations involve the use of the usual 
number of wooden ties laid in concrete. This construction has 
been adopted as shown in Fig. 71 in Chicago, where it has been 
the policy to construct a permanent foundation from which the 
rails may be removed from time to time and new rails installed. 
This rigid construction of the roadbed is at variance with the 
method of at least one of the largest steam roads whose engineers 
believe that the roadbed construction should be somewhat 
flexible in a vertical plane, being depressed slightly as the train 
passes, but returning to its original position thereafter. 

Rail Joints. — Aside from the mechanically rigid rail joints 
produced by cast welding, thermit welding and electric welding 
discussed in some detail in Chapter VI, Part II, several other 
types of rail joints in rather more common use should be men- 
tioned. The simplest and cheapest joint is of course the four 
or six bolt fish plate clamped on either side of the rail ends. This 
construction allows considerable vertical motion to the ends 
of the rails as the train passes over them, causing the heads to be 
soon flattened. The rail must therefore be replaced or shortened 
because of its worn condition at the end before it is seriously 
worn elsewhere. 

The other types of joints most commonly used are the Atlas, 
Continuous and Weber joints, all of which make use of combined 
splice bars and tie plates differing but slightly in design, i.e., they 
all furnish an iron plate between the foot of the rail and the tie, 
which plate is generally notched to receive the spikes in order 
to prevent creeping. The Weber joint makes use of a single 
plate cast in one piece with one of the vertical plates while the 
other joints involve two half plates split longitudinally under 
the center of .the rail. 

The use of tie plates is a matter open for discussion. They 
probably increase the life of the ties, especially when rather soft 



214 ELECTIRC RAILWAY ENGINEERING. 

wood is used, by preventing chafing between rail and tie, but 
many engineers are not convinced that this gain warrants the 
extra expense. 

Rail joints may be of the '^suspension" or "supported" type, 
the former having the rail ends between ties, while the latter 
provides a tie directly under the ends of the rails. The former 
seems to be in more general use. In case the Atlas rail joint be 
selected the suspension type must be used, as this joint requires 
transverse bolts through the casting under the rail flanges at the 
end of the rail. 

Both 30 and 60 ft. rail lengths are in use, the former being 
preferred in interurban construction because of less expansion 
troubles therewith and the greater ease of handling the shorter 
length on curves. Where the above features are not objectionable, 
however, the 60 ft. rail has the advantage of fewer joints and 
bonds, thereby reducing slightly the first cost and maintenance 
charges. 

Rail Corrugation. — Quite recently a peculiar corrugation of 
the heads of rails, particularly near the joints, has been reported 
by many companies and in many instances special grinding de- 
vices have been designed to remove such corrugations, but in spite 
of extended study and discussion of the question no satisfactory 
reason for the effect has been found. It has been variously 
attributed to chattering of brake rigging upon stopping the car, 
the transverse nosing of trucks, the peculiar chemical or mole- 
cular structure of the rails and the possible formation of succes- 
sively soft and hard spots due to some peculiarity of the rolling 
process. As this effect has been found under practically all 
conditions, rails of one particular make or in any particular posi- 
tion in the roadbed cannot alone be charged with the difficulty. 

Paving. — The railway company is usually required to install 
and maintain the pavement between tracks and for a distance of 
2 ft. or more outside. If paving blocks are used with anything 
but a 9 in. girder rail a special block must be secured to fit the 
rail and provide a groove inside the rail sufficient to allow the 
wheel flange to pass without forming a dangerous rut for vehicular 
traffic. Such grooves are rapidly worn away by the latter traffic 
and the railway company endeavors, therefore, so to design the 



TRACK LAYOUT AND CONSTRUCTION. 



215 



track and paving that the vehicles will not be attracted thereto. 
This policy will often aid in making schedule time in city streets 
as well. With the grooved girder rail the groove provides room 
for the flange. Fig. 71 well illustrates paving construction with 
this type of rail. 

; Galv. Through Bolts 
! >./x 2^i X ?^5 Galv. W.I. Washers 
[— G Rake i;_ in 24 from Top of Rail 

z IG Braces Galv. 
, It II 

iFor llOCO Volts Use i\i x ^^^ H.P. Cross Arms 

ll)4''x 1>a"x i'Top LooQSt Pins 
For 22000 Volts Use 33^ s 1% H.P. Cross Arms 
ffi/ 11 13 X \%s. l%"Top Locust Pins 




Fig. 82. 

Overhead Construction. — Typical bracket and span overhead 
construction are now so familiar to all, little description is neces- 
sary aside from the specifications given in Fig. 82 and ^t,, the 
former representing the single track bracket standard construc- 
tion of the Connecticut Company, while the latter is typical of 
double track span construction whh two high tension trans- 
mission lines. 

Neither of the above illustrations, however, shows the details 



2l6 



ELECTRIC RAILWAY ENGINEERING. 



of the trolley insulation and hangers. It is customary at pres- 
ent to use grooved hard drawn trolley wire with mechanical 
clamps or ears which spring into the grooves in the wire and are 
clamped therein by means of four machine screws. Much time 
is thus saved in repairs over the old soldered ears. Double 
insulation is provided between pole and trolley by means of the 
insulating hanger and strain insulators in series. Strain insu- 
lators in span construction should be sufficiently near the trolley 




Fig. 83. 

so that a broken ''live" span cannot reach the ground and yet 
sufficiently far away so that a trolley pole when off the wire cannot 
impress full potential upon the span outside the strain insulator. 

Catenary line construction, which is meeting with favor even 
for low voltages, was described in a previous chapter. 

Lightning protection is provided for the trolleys and feeders 
by mounting a low voltage lightning arrester on the pole top at 
distances apart varying with different companies from 1000 ft. 
to several miles. Grounds for such arresters should be thor- 
oughly made by burying a plate of copper or an amount of scrap 



TRACK LAYOUT AND CONSTRUCTION. 21 7 

copper wire of large surface area in coke in permanently moist 
earth and connecting the arrester with this ground by means of a 
straight copper wire of at least No. 4 B. & S. with well soldered 
joint stapled to the pole. Fairly good results have been obtained 
in new construction by winding copper strip about the butt of 
the pole before installation and in some cases with a long pipe 
driven into the ground containing a plug into which the ground 
wire is soldered. The practice of grounding lightning arresters 
to the rails should be discontinued as it has been found to destroy 
the arresters without giving the necessary protection. 

Poles are usually spaced from 80 to 125 ft. apart, the smaller 
distance being used on curves. Poles should be guyed on curves 
and anchors or longitudinal guys installed to support the line at 
least every mile. With the present cost of lumber it seems worth 
while to treat the butts at least with preservative compound 
and often to treat the entire pole. The poles should at least be 
kept well painted even on inter urban lines. Iron poles have 
found a place in city streets principally because of their better 
appearance. Corrosion can be held in check by painting fre- 
quently and by setting butts in concret€. In fact, the latter 
method is often used for the protection of wooden poles even 
after they have begun to decay at the surface of the ground. 

Estimates. — Whereas the cost of materials varies so greatly 
in different portions of the country, estimates or actual costs of 
construction must be taken with a great deal of caution. They 
seem to be of sufficient value as a study of approximate relative 
values, however, to warrant listing herein. Such an estimate 
covering the construction for an interurban line 63 miles in 
length in the South will therefore be found on page 218. 

The estimate represents an expenditure of $13,700 per mile for 
roadbed and track exclusive of engineer's fee and contractor's 
profit. It is interesting to note that of the above total 37.8 per 
cent, is labor and 62. 2 per cent, material. 



2l8 



ELECTRIC RAILWAY ENGINEERING. 



ESTIMATED COST OF ROADBED CONSTRUCTION. 



Labor. 



Material. 



Total? 



Clearing and Grubbing. 

68 acres at $45 

Grading. 

Solid rock 8000 yds. at $0. 75 

Loose rock 35000 yds. at $0.37 

Earth, 716000 yds. at $0.145 

Culverts. 

150 Culverts varying from 18'' to 60" diam. 
Total 4573'. 

Hauling and placing 

End walls 1300 yds. at $8 

Timber bridges. 

41 Pile bridges, 4752 lin. ft. at $8 .80 

I Frame bent bridge, 800 lin. ft. at $10.25 . . 
Steel Bridges. 

9 Steel spans ranging from 30' to 130', 
700520 lb. erect, at 4 1/8 cents. 

Concrete piers, 2300 yds. at $7.20 

Deck, 2300 yds. at $2 . 50 

Track. 

Rail 80 lb. 2,2)' ^ 8431.7 tons at $33.515 

Angle bars, 21690 prs. at .86 

Track bolts, 86762 at .04 

Track spikes, 2010 kegs at $5.60 

Bonds, 2 1 160 at .60 

Cross bonds 67 total 

Track ties, 169860 at .65 

Switches compl., 18 at $150 

Labor 

Ballast. 

Local gravel or lime rock 

Fencing {Wire). 

26900 rds 

Miscellaneous. 

Railroad crossings at $300 

Highway and Private crossings at $47 

Signs 




26,548 



130,000 
5,380 

200 

1,150 
100 



Grand total. . 



468,921 



130,000 

11,112 I 16,492 
I 
1,000 j 

4,490 

300 7,240 



CHAPTER II. 
Rolling Stock. 

Notwithstanding the fact that electric traction has been de- 
veloped within a comparatively few years, cars which are now 
operated upon the various city and interurban lines of the country 
range from the 20 ft. single-truck made over horse-cars to the 
60 ft. magnificent limited double-truck parlor cars weighing from 
40 to 50 tons and provided with all the conveniences of the 
Pullman coach. With this array of possible rolling stock to 
choose from the problem of car selection for a proposed road or 
for additions to present equipment on city or interurban systems 
is a difficult matter. Too little attention has been given to this 
problem in the past, the questions of sufficient seating capacity 
and finish often being the principal considerations in the selection 
of cars. These factors are of course of prime importance, for the 
public patronage is not only dependent upon the ability to obtain 
a seat in a car, especially upon a long journey, but also to a sur- 
prising extent upon the appointments of the cars with respect to 
personal convenience. That there are several other very im- 
portant factors to be taken into account, however, will be made 
clear in the following discussion. 

With the gradual increase in speed of cars there came an 
increasing number of wrecks which soon proved the average 
car construction to be unsuitable for withstanding severe strains 
and thereby protecting passengers to some extent from injury in 
case of collision. Then came a period of marked increase in 
the weight of cars with correspondingly increased capacity of 
car equipment not only, but of feeders, and substation and power 
station capacity as well. Quite recently, however, another 
reaction has taken place, for it has been found that the desired 
strength to resist the abnormal forces in service may be obtained 
by proper design with even less weight. This apparently para- 
doxical condition is partly due to the fact that the use of steel in 

219 



220 



ELECTRIC RAILWAY ENGINEERING. 



place of wood will give greater strength with less weight and also 
for the reason that a car may be considered as a double truss, 
the side frames acting as one truss to transfer the load to the 
bolsters and the bolsters in turn acting as transverse trusses 
between the car sills and the truck support. For steel frame 
construction see Fig. 84. 

The desirable reductions possible in cost of power, car repairs, 
track repairs, fixed charges on power plant and distribution 




Fig. 84. 

system with decrease in weight of cars are very clearly pointed 
out in a paper by M. V. Ayers, electrical engineer of the Boston 
& Worcester Street Railway before the American Street and 
Inter urban Railway Engineering Association in 1909. In this 
paper formulae are developed for the above cost reductions and 
suggestions given for the possible decrease in weight of cars 
without a curtailment of strength. Aside from the above truss 
design and steel under framing, the use of aluminum and cast 
bronzes in place of iron, soft woods in many places instead of 
hard woods and the reduction in the weights of motors with 
forced ventilation are mentioned. 



ROLLING STOCK. 221 

Another very marked advance is the standardization by the 
above association of the heights of underframes of both inter- 
urban and city cars and the use of corrugated iron buffers on the 
latter extending to the height of the sills of the former cars to 
prevent telescoping of platforms in case of collision. Such 
telescoping was the cause of much damage in several recent and 
very serious interurban wrecks in the Middle West. 

Motor Equipment. — The question of whether a two or four 
motor equipment should be installed must be given careful thought. 
Previous chapters have described the method of determining the 
total power required for the car, but whether this should be sup- 
plied by two or four motors is quite another problem. With 
single truck cars two motors only are possible. In the case of 
double truck cars four motor equipment is probably most com- 
monly found, although many roads are operating with but one 
motor per truck. Tests which have been made with the same 
car equipped in both ways disclose the fact, which might be 
theoretically predicted, that the four motor equipment will re- 
quire less power for the same schedule. This is largely due to 
the distribution of torque over the larger number of driving 
wheels. This torque distribution as well as the reserve capacity 
over that called for by the theoretical calculations, especially 
under the abnormal conditions of snow fighting and making up 
lost time, are usually considered of tangible monetary value by 
traction managers. 

For these reasons the four motor equipment has generally 
found favor. While the control equipment and car wiring are 
slightly more complicated with the four motor equipment the 
ability to use two motors, ordinarily with one on each truck, in 
case of failure of one or more of the other set is worthy of con- 
sideration. In short the continuity of service and maintenance 
of schedule speed must be thought of as well as first cost of equip- 
ment and operating expense. 

Trucks. — The truck primarily consists of two pairs of wheels 
and axles upon whose journals a steel framework is supported 
by means of combined spiral and elliptical springs. This frame- 
work serves to take the weight of the car body not only, but to 
form a support for the brake rigging and a portion of the weight 



222 ELECTRIC RAILWAY ENOmEERING. 

of the motors as well. Since the axles are held in a position par- 
allel to each other by the fixed journal boxes the distance between 
axles cannot exceed a certain value, generally 7 ft. 6 in., because 
of difficulties in following curves of short radius in the track. 
With this limitation and with the further fact demonstrated by 
practice that single truck cars tend to rock badly in the direction 
of motion, the length of single truck car bodies must necessarily 
be limited to from 22 to 25 ft. overall. For the longer cars two 
trucks with king pins located as near the ends of the car as pos- 
sible without interfering with vestibule supports must be used. 

With either type of truck the motors are suspended with two 
babitted boxes, cast in one side of the motor frame, bearing on 
the car axle and the opposite side of the motor is hung by means 
of a flexible link from the truck frame. The so-called "nose" 
suspension provides but one support between motor and frame, 
while the "yoke" suspension, as the name implies furnishes 
two such connections. With these suspensions the motor 
is permitted to swing slightly about the car axle as a center as 
the car passes over irregularities in the track, thus keeping the 
pinion on the motor shaft at all times in mesh with the gear on 
the car axle. 

Trucks are provided with car wheels ranging from 33 to 37 in. 
in diameter, the larger sizes being generally used in heavy inter- 
urban traction. Wheels are constructed of cast iron with chilled 
treads, cast steel, or a combination of cast iron centers with steel 
rims. The latter type has now been largely replaced on inter- 
urban roads by the cast steel wheel, as some difficulties were 
encountered due to the steel rims working loose in service. 
Wheels may be returned four or five times before scrapping is 
necessary, a reduction of from 3/4 to i in. in diameter being 
possible before wheels must be discarded. Steel wheels will 
range from four to five times the mileage of cast iron wheels and 
the latter are considered unsafe above 30 m. p. h. Wheels vary- 
ing as much as 2 in. in diameter have been successfully used on 
different axles of the same car, although those on the same axle 
must be of the same diameter. The wheels are forced on the 
axles under hydraulic pressures of from 25 to 50 tons, depending 
upon the type of wheel and size of axles. 



ROLLING STOCK. 223 

Car axles are turned from cold rolled steel and vary in diameter 
from 4 in. with the smallest motors up to 7 in. with 200 and 250 
h. p. motors in heavy service. 

Lubrication is ordinarily provided to the half bearing by means 
of cotton waste soaked in grease with which the journal box is 
packed, although within the last few years an apparent saving 
has been made on some roads by adapting the journals to oil 
lubrication. 

Trucks are provided with side bearing plates upon which 
similar plates on the under side of the car may rest when the 
latter is unequally loaded or upon curves to prevent too great 
tilting of the car. 

Lighting. — The very unsatisfactory nature of car lighting at 
the present time, especially upon interurban roads, has been 
commented upon in a previous chapter. The reason for this in 
the face of public criticism on roads where everything else is done 
for the convenience and comfort of the passengers is difficult to 
understand. The present method of lighting is that of using 
several series of five incandescent lamps each protected by fuses 
and connected directly between the trolley and ground so that 
the lights will not be extinguished when the circuit breaker opens. 
Several clusters are distributed throughout the hood of the car 
and often a light is placed over each seat. The incandescent 
headlight, if one be used, may be lighted in place of the vestibule 
light on the front end of the car by means of a snap switch. All 
the lights are, of course, dependent upon trolley voltage which 
has been previously shown to vary over a wide range with more 
than proportional variations in light intensity. A lighting 
system independent of trolley voltage must sooner or later re- 
place this unsatisfactory method of car lighting. 

Arc headlights are generally used on interurban lines with 
some provision for operation upon city streets such as a gauze 
shade, reduced voltage, polarity reversal in the case of the mag- 
netite arc or the substitution of an incandescent lamp. These 
headlights require from 4 to 4 1/2 amperes at 550 volts, of which 
over 80 per cent, is wasted in external resistance. 

Heating. — City cars and some of the smaller interurban^Vars 
are heated by means of electric heaters provided with switches 



224 ELECTRIC RAILWAY ENGINEERING. 

located in the vestibule which will permit several degrees of heat 
by changes of the heater coils from series to parallel grouping. 
The problem of car heating, especially upon long exposed runs at 
high speed in the coldest weather is a serious one, a car requiring 
from lo to 30 amperes at 550 volts for such service. One large 
city railway system in particular, although able to supply the de- 
mands of summer traffic with existing power station equipment 
was forced to install additional apparatus and enlarge its station 
in order to meet the car heating demand in winter. 

Interurban companies and especially those operating single- 
end cars have adopted the hot-water heating system almost 



Fig. 85. 

exclusively, the heater being located in one end of the car, pref- 
erably in the baggage compartment or motorman's cab. This 
system has the double advantage of low cost of operation and 
more even distribution of heat in the car, this being accomplished 
by means of pipes encircling the car near the floor as in the case of 
the cars of steam railroads. 

Current Collection. — Little change has been made in the 
overhead trolley since the earliest days of electric traction, its 
operation being entirely satisfactory except for the very highest 
speeds or for the collection of very heavy currents. Large trolley 
wheels are used for high speed service and each road has a par- 
ticular composition for the wheel casting which is believed to be 
best for local conditions. Wheels should run from 5,000 to 
10,000 miles before replacement is necessary. 

The pantograph bow collector is coming into general use in 



ROLLING STOCK. 



225 



high voltage high speed service. Such a device is illustrated 
upon a car in Fig. 85. It is raised to the wire by air pressure, 
the controlling valve being in the motorman's cab. With this 
type of collector the alignment of the trolley wire is not important, 
as the collector is often two or more feet in length and any trans- 
verse movement prevents local wearing of the collector. 




Fig. 86. 



The third rail shoe for collecting heavy currents from the 
third rail mounted beside the running rails has been referred 
to previously. A view of one of the many types may be found 
in Fig. 86. Some difficulty has been encountered in the past 
with this construction in winter for if sleet be allowed to form on 
15 



2 26 ELECTRIC RAILWAY ENGINEERING. 

the rail the shoe tends to ride on the sleet and a poor contact with 
much arcing results. Various methods have been devised to 
overcome this difficulty with more or less success. Those most 
used are a steel brush or scraper placed ahead of the shoe and 
sprinkling the third rail with brine. 

Car Wiring. — A great deal of laxity has existed in the past in 
regard to car wiring and many accidents and fires have resulted 
in consequence. As the Underwriter's Code does not rigidly 
apply since cars are not insured, the tendency has been to use 
little care in running the wires under the car. Rubber covered 
wire is of course used, but it is customary to group all the wires 
together in one or two cables in a length of canvas hose hung 
from the car sills and extending from motors to controllers. The 
cable extending from the trolley base is supported on the top of 
the car roof by means of brass clips and is carried either into the 
car vestibule to the circuit breaker with only the insulation of the 
wire or, in the case of master control, it is carried down one of 
the corner posts of the car in moulding. 

Recently the Fire Underwriters have drawn up a code of rules 
for car wiring and many improvements have resulted therefrom. 
Asbestos lined conduit is now often laid under the seats of the 
car for the installation of cables while in the best construction, 
used especially in subway cars, iron conduit is installed as in 
building wiring. Present practice also involves asbestos lumber 
or galvanized iron protection between wiring and wooden car 
frames, especially over the rheostats. Car wiring diagrams will 
be considered under "Types of Control," Chapter IV. 

Special Types of Cars. — The above discussion applies to all 
types of cars. The special features of cars designed for a par- 
ticular service will be outlined below. 

City Cars. — In the smaller cities where traffic is not particu- 
larly heavy the 20 ft. single truck car with longitudinal seats is 
still used. The corresponding summer equipment would be a 
20 ft., ten bench single truck car with running board. Officials 
differ as to the advisability of maintaining a double motor equip- 
ment and many of the smaller roads shift the equipment twice a 
year from one type of car to the other. With single trucks this 
involves considerable labor, but if double trucks be used the 



ROLLING STOCK. 227 

trucks complete with motors can be changed with little trouble. 
Where summer traffic is heavy, especially to summer resorts, 
the 35 ft., 15 bench, double truck open cars or small trailer cars 
are used. 

In the large cities the convertible or semi-convertible double 
truck cars. Fig. 87, with either transverse seats throughout or a 
combination of transverse and longitudinal seats are adopted, 
the same cars being used throughout the year. This avoids 
duplication of equipment and the dangers incident to the opera- 
tion of the running board type of car in congested districts. Cars 
with transverse seats are much more • comfortable, especially 



^^ 


sd 


Sffr 


E^iiiiii 


Wy iW'' ::W'-'- '^ 


nsu 


H|-iil-''"" ' -^-' 




■■ dHH^ 


Lj.- 7-----^ ] 




1 iiw^Hfl 




^^^1 



Fig. 87. 

for long rides, but they do not permit rapid ingress and egress, 
nor do they provide the standing room for a given size of car 
that the longitudinal seats furnish. The combination of both 
types of seats for long cars with the section of transverse seats in 
the center of the car permits the long-haul passengers to ride in 
comfort and yet furnishes more readily accessible seats and 
standing room for the local traffic. 

Pay as You Enter Cars. — This type of car which has been 
quite recently adopted in the large cities with considerable suc- 
cess has the advantage that the conductor may always remain on 
the rear platform to start and stop the car promptly and to avoid 
possible accidents. The probability of obtaining all the fares 
when traffic is heavy is also increased. An apparent disadvan- 



228 



ELECTRIC RAILWAY ENGINEERING. 



tage is the increased length of stop, but this has not proved to be 
serious as the platforms in this type of car are very large and 
when this platform is filled the car is started. The fares are 



Sign,"Plea3« psy as you gst on" 

c 



Entrance 
i„/,i'/=i Door 




t-e 8'2— --^^ 



-27 7- 



—42 3- 
FlG. 





Fig. 89. 

paid before the passengers enter the car, but during the period 
the car is in motion. This procedure, together with the time 
saved by the conductor being in' a position to start the car 
promptly has permitted the same schedule to be maintained in 



ROLLING STOCK. 



229 



several cities with less cars where this type of car has been 
adopted. A plan view of this type of car will be found in Fig. 
88, while the method of paying fare is well illustrated in Fig. 89. 
These cars are almost invariably designed for single end operation. 
Suburban Cars. — This service in large cities is maintained 
with the semi-convertible car of the double truck type, in some 




Fig. 90. 

instances with the addition of vestibule doors operated by com- 
pressed air controlled by the motorman. With this equipment, 
the motorman is required to close all the doors of the car after 
the starting signal has been given, but before the car is started. 
In most installations of this type of car the car step is hinged and 
so connected with the doors that it is folded up as the door closes. 
This successfully prevents attempts to board cars when in motion. 



68 i Orer Bumpers 



^''3^u u u Ui 



1 s 4() Ureep 
[>oor CUass above 



Smoking 



=C0-»3 






loturman'a Calj -4 




Dwmnwnp 

" t- Main Cumpartment Heatei 



-i2's^"- 




FiG. gi. 



Open running board cars are used much more in the East 
than in the Middle West for suburban service. Such a car 42 ft. 
6 in. in length and weighing 13 tons without electrical equipment 
is shown in Fig. 90. 

Interurban Cars. — Cars which have been developed for 
interurban service which has recently grown so rapidly, particu- 



230 



ELECTRIC RAILWAY ENGINEERING. 



larly in the Middle West, are patterned after the steam railroad 
coaches and often reach lengths of 68 ft. and weights of 50 tons. 
These cars are equipped with transverse seats and are divided 
into four compartments, for motorman's cab, baggage, smoking 
and main passenger service respectively. This design of course 
precludes double end operation, A plan view of such a car may 
be seen in Fig. 91, while a similar car designed as a sleeper and 




Fig. 92. 

operated upon the Illinois Traction Company's lines between 
St. Louis and Peoria, Illinois, is illustrated in the plan view of 
Fig. 92. 

Elevated and Subway Cars. — In the elevated and subway 
service in the largest cities a slightly different type of car is re- 
quired, although it is patterned closely after the interurban car. 
Exits are so located as to be flush with the platform floors, no 




Fig. 93. 

steps being necessary. In Boston and New York both side and 
end doors are provided and with the traveling public trained to 
enter by the end door and leave the car by the side door, some 
time is gained at the station. Both transverse and longitudinal 
seats are provided. These cars are designed to operate in trains, 
each train consisting of both motor cars and trailers, all motor cars 
being operated by means of the multiple-unit control from the 



ROLLING STOCK. 23 1 

motorman's cab of the forward car. In the New York subway 
steel cars are now being adopted, one of this type being illus- 
trated in Fig. 93. 

While the life of cars will vary from ten to twenty years, de- 
pending upon the type, severity of service and the attention 
which they receive in the shops, obsolescence has been the reason 
for discarding most of the cars used thus far, i.e., traffic demand 
has required that larger and better cars replace those in operation 
before the latter were actually worn out. 



CHAPTER III. 
Motors. 

Much of the theory underlying the operation of the direct 
current series motor has been discussed in a previous chapter. 
A brief outline of their construction and selection together with 
the principle of operation of the alternating current motors used 
in railway systems will be herein considered. 

Direct Current Motor. — The direct current series railway 
motor, Fig. 94, differs from the stationary type principally in the 
design of the frame, that of the former motor consisting of a box- 
like iron casting split in a plane through the center of the shaft 




Fig. 94. 

and hinged in such a manner that the lower half of the frame 
with two field poles and windings may be lowered for inspection 
of the armature with the motor in place on the truck. The larger 
motors are of the so-called "box" type with the frame in a single 
casting. The armature is removed from this motor by taking off 
the end bearing plate and drawing the armature out in a direction 
parallel with the shaft through the opening thus made. The 
motor must be removed from the truck for this operation. The 
frames of both types of motors are provided with openings and 

232 



MOTORS 233 

moisture-proof cover plates for ready access to armature, com- 
mutator and connecting cables. These cables are brought out 
through insulating bushings in the frame of the motor, which are 
usually located on the side next to the truck bolster, in order that 
the movement of these cables may be least when rounding curves. 

Railway motors are generally of the four pole type with the 
axes of the poles at an angle of 45° with the horizontal in the split 
frame types. Field coils are wound with rubber or asbestos 
covered wire with asbestos insulation between layers or in the 
larger motors with copper strip. The coils are taped, impreg- 
nated with insulating compound with the vacuum process and 
waterproofed. 

Two sets of bearings are provided in the frame, one pair for the 
car axles and the second for the armature shaft. These are 
of babbit lined cast bronze. 

The armature and commutator are not unlike those of station- 
ary motors except that the armature is series wound and requires 
but two sets of brushes. These are placed on the top portion 
of the commutator and are therefore accessible through trap 
doors in the floor of the car. The brush holders are fixed in 
position and support the carbon brushes in a radial position on 
the commutator so that the motor may operate equally well in 
either direction. 

Conimutating Pole Motors. — As in the case of direct current 
stationary motors and generators, the rather marked advantages 
of the commutating pole are applied to the railway motor. These 
commutating poles are auxiliary poles provided with a winding 
connected in series with the armature. As the magnetic flux 
in these poles will vary with the armature current the serious 
effects of armature reaction upon commutation are neutralized 
at all loads by the flux from these auxiliary poles. The latter 
are so designed and located that the short circuit current in the 
coil under the brush is small and sparking at the brushes there- 
fore a minimum. As the output of the motor is often limited by 
commutation as well as temperature rise, the overload capacity 
will be increased and its maintenance cost reduced. It is 
claimed that 100 per cent, overload may be suddenly thrown on 
and off such a motor without sparking at the brushes. 



234 ELECTRIC RAILWAY ENGINEERING. 

Single Phase Motors. — With the increase in length of inter- 
urban lines and their large power demands together with the 
realization of the high first cost and maintenance charges on the 
converting equipment necessary for long direct current roads, 
came the serious study of the possibilities of alternating current 
motors for railway use. It was at once recognized that if a 
satisfactory alternating current railway motor could be developed 
considerable saving could be made in the above factors and a 
marked simplification in the distribution system effected, as 
pointed out in the chapter on the distribution system, to say 
nothing of the possible reduction in distribution system losses 
due to the increase in trolley voltage. As the polyphase motors 
which have been developed were of the constant speed type 
with inherent characteristics unfavorable for traction and since 
the advantages of polyphase transmission at high voltage can 
be gained without the complication of a polyphase distribution 
system and car circuits, the attention of American engineers was 
first turned to the development of the single-phase motor for 
traction purposes. 

This development may be approached either by endeavoring 
to adapt the direct current series motor, whose characteristics 
have proved satisfactory for traction purposes, for use upon 
single-phase alternating current circuits or the alternating current 
induction motor may be studied with a view toward redesigning it 
for railway use. Both of these viewpoints will be considered in 
the order mentioned. 

Adaptation of the Direct Current Series Motor. — Those 
familiar with the direct current motor will remember that a 
reversal of the current in either armature or field alone will 
reverse the direction of rotation of the motor, whereas a reversal 
of both field and armature connections will not change its direc- 
tion of rotation. It might be predicted therefore that when a 
direct current series motor is connected to an alternating current 
circuit of proper voltage, the motor would operate. This was 
found to be the case, although many effects of the alternating 
current, which are discussed below, cause the motor to operate 
unsatisfactorily from a practical standpoint unless several changes 
are made in its design. 



MOTORS. 



235 



The e. m. f. impressed upon a direct current series motor is 
balanced by the sum of counter e. m. f. of revolution (E^.) and the 
(IR) fall of potential in field and armature windings. In addition 
to these there exists in the series motor operating upon an alter- 
nating current circuit the reactive voltage of the series field and 
armature windings. 

The reactive voltages are due to the self induction of the re- 
spective windings or better to the cutting of the conductors by 
the lines of leakage magnetic force which encircle one set of con- 
ductors only and are therefore not useful in producing counter or 





^^^ 


/^ 


^ 






/ 


' ir; 


^ \ 






IXa 


E. 




' ir/ 





Fig. 95. 

energy electromotive force. This voltage is 90° in advance of 
the current and may be treated as though there were an external 
choke coil of corresponding reactance connected in series with 
the motor. It is directly proportional to the frequency of the 
voltage supply. 

With these voltages in mind the vector diagram of the motor 
may be drawn as in Fig. 95 where 

E = Impressed voltage. 
Ey = Counter e. m. f. of revolution. 
I = Current in armature and field. 
R^ = Resistance of armature. 
X^ = Reactance of armature. 
Rf = Resistance of field. 
Xf = Reactance of field. 
=^ Angle between impressed voltage and current 
whose cosine is the power factor of the motor. 



236 



ELECTRIC RAILWAY ENGINEERING. 



From the diagram it will be seen that any change of design 
that will reduce (Xf) and (XJ will increase the power factor of 
the motor. This is a desirable change as a higher power factor 
results in smaller losses and higher torque in the motor not only, 
but either lower losses or less copper in the distribution system 
as well. The reactance voltage of the armature (IX J may be 
more or less completely neutralized by means of a compensating 
winding which will be subsequently explained, while that of the 
field can only be reduced by reducing the turns on the field or 
the magnetic induction. 

Before these possible changes are studied further the question 
of commutation may well be investigated, for the commuta- 




FlG. 96. 

tion of a direct current motor operating upon alternating current 
is noticeably poor. It will be remembered that in the commu- 
tation of direct current motors, care must be taken to have the 
current a minimum in the coil or coils which are short circuited 
by the brushes in order that the spark which occurs when the 
coil is disconnected from the brush by the movement of the com- 
mutator may not be serious. Reference to Fig. 96 will show, 
however, that there is an additional factor to be considered in the 
commutation of an alternating current motor. The motor is 
quite similar to a transformer in that it has a magnetic circuit 
surrounded by two sets of coils, the field and the armature. The 
pulsating flux set up by the field generates an electromotive force 
due to this transformer action in the coils of the armature, those 
coils in the plane (a'b') which enclose the greatest number of 



MOTORS. 237 

magnetic lines of force generating the highest voltage and those 
in the plane (ab) theoretically zero voltage. But one or more 
of the coils in plane (a'b') are short circuited by the brushes. 
A large current flows through this coil therefore as in the case of 
a short circuited secondary coil on a transformer. Unless the 
design is altered so as to reduce this current, vicious sparking will 
take place and seriously limit the commutating capacity of the 
motor. 

Two methods of reducing this short circuit current are in 
general use. One makes use of an auxiliary coil placed 90 elec- 
trical degrees from the field coils as in the case of the commutating 
poles on direct current motors. This so-called "compensating" 
coil is in series with the armature and is designed of such strength 
as to neutralize the combined effect of transformer e. m. f. and 
arniature reactance e. m. f. While such a coil can be made to 
perform such neutralization for one load and partially neu- 
tralize the e. m. f. on all loads, its effect is not complete over the 
entire range of load, it being particularly faulty at very light loads. 
One of the large manufacturing companies overcomes this light 
load fault by inserting "preventive" leads between the point 
where connection is made between armature coils and the com- 
mutator. These leads are of relatively high resistance and 
therefore tend to limit the short circuit current to a minimum. 
As the current circulating through the armature coils encounters 
the resistance of the preventive leads only as it flows into or out 
from a brush, the heat loss in the leads is not large. The com- 
bination of compensating coils and preventive leads not only 
puts the commutation of the alternating current series motor on 
a par with that of the direct current mptor, but it increases the 
power factor to a practical operative value as well. 

Returning to the question of reducing the reactance e. m. f. 
of the field in order that the power factor may be still further 
increased. If this be done by reducing the field flux, the capacity 
of the motor is correspondingly lowered. It is actually accom- 
plished in practice, therefore, by reducing the number of field 
turns to from 20 to 25 per cent, of those in a direct current motor 
of similar characteristics. This is rather difficult with the large 
capacity motors having a relatively large number of poles. 



238 ELECTRIC RAILWAY ENGINEERING. 

Aside from the above changes in design which are necessary 
in order to adapt the direct current motor to use with alternating 
current, the field must be laminated as well as the armature to 
prevent serious eddy current losses. The reluctance of the 
magnetic circuit must be reduced in order that the flux may not 
be sacrificed with a smaller number of field turns and joints are 
therefore eliminated and the sectional area of the poles increased. 
Theoretically the length of the air gap might be shortened to 
produce the desired reduction in reluctance, but this is not con- 
sidered advisable from a practical operating standpoint, for with 
the direct current motors the bearings often wear to such an ex- 
tent that the armature rubs on the lower field poles. 

Adaptation of Induction Motor. — The evolution of the single 
phase induction motor into the alternating current series railway 
motor has been very clearly explained from the theoretical stand- 
point by McAllister.^ Briefly the development is as follows: 
Suppose a single-phase induction motor stator to be provided 
with an armature similar to that of a direct current series motor 
and the stator and armature windings to be connected in series. 
McAllister shows very clearly that with all possible ratios of field 
to armature turns the power factor will not exceed 45 per cent. 
and the maximum limit of the ratio of starting to synchronous 
torque will be in the neighborhood of 125 per cent. Both of these 
values are too small for a satisfactory railway motor. 

If the reluctance of the air gap between polar regions be in- 
creased by forming polar projections in the stator fields such that 
the ratio of reluctance of the leakage path between poles to that, 
under the poles may be considered as infinite, the power factor 
and torque ratio may be increased over a wide range by properly 
proportioning the armature and field turns. The successful 
railway motor may be considered, therefore, as an induction 
motor stator with projecting poles enclosing an armature similar 
in design to that of a direct current series motor. 

Construction of the Single-phase Motor. — As the result of 
the above studies a motor has been developed which is giving 
very satisfactory results upon single-phase railway systems of 

^ Alternating Current Motors by McAllister. 



MOTORS. 



239 



low frequency (25 cycles) especially in the larger sizes which have 
been applied to locomotives. 

Such a motor, Fig. 97, does not appear materially different 
from the direct current motor, consisting of a cast steel box type 
frame supporting the laminated iron stator which is so punched 
as to form polar projections. These are, however, shorter than 
in the direct current motor. The motors are provided with four 
or six poles and their field windings are of the distributed type 
similar to those of the single-phase induction motor. The wind- 




FiG. 97. 



ing is of heavy strap copper, however, and consists of a relatively 
few turns. Between the main field windings are located the 
compensating windings connected in series with the armature. 
The armature is practically identical with that of the direct cur- 
rent motor with the exception that because of the lower voltage 
and consequently higher current for which it is designed it is 
usually necessary to provide one set of brushes for each pole. 

Characteristics. — The characteristics of the single-phase 
motor are strikingly similar to those of its competitor, as will be 
seen by comparing Figs. 98 and 13. The efficiency of the former 
motor is slightly lower and the torque-current curve slightly more 



240 



ELECTRIC RAILWAY ENGINEERINC^. 



concave owing to the lower induction for which the alternating 
current motor is designed. With the fields unsaturated, therefore, 
the torque will vary with the square of the current. 

Operation on Direct Current. — One of the most important 
features to commend the single-phase series motor as above 
described is its satisfactory operation on direct current circuits. 
If the changes which have been made to adapt the motor to alter- 































Ph' 
































CHARACTERISTIC CURVES 

OF 125 H.P. SINGLE PHASE 

25 CYCLE A.C. MOTOR ,, 
DIAMETER OF WHEELS37V2 
GEAR RATIO 2.33 






Oh ^ 

^ 0) 










cr. 

Speed 
3r Cent Effici 




























































/ 


pH 
50 100 

90 
W 80 

TO 
30 60 

50 
20 












s. 












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PotW j 


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10 










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_y> 


y 


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100 



300 



300 400 
Amperes 

Fig. 98. 



500 



600 



u 
o 



2400 



2000 



1600 



1200 



800 



400 



700 



nating current are reviewed it will be noted that no change made 
impairs its use with direct current. Since it is highly important 
that interurban roads operate their cars to the center of the termi- 
nal cities over the existing direct current trolley, this feature of the 
series alternating current motor is of greatest value. Whereas 
the control system must be duplicated to some extent, as will 
be seen in the next chapter, the flexibility of operation is well 
worthy of the slightly added complication. 



MOTORS. 



241 



Repulsion Motor/ — When it was found that a corrective 
current could be made to flow in the armature of an alternating 
current armature by means of induction between windings as in 
the case of the transformer, it was inferred that such a current 
might be made to produce a torque without connection between 
armature and field as in Fig. 99. Such a motor was found to 



Series Field 




Compensating 
Field 



Fig. 99. 

operate satisfactorily, the brushes being short circuited to allow 
the torque producing currents to flow in the armature windings. 
The characteristics of such a motor are similar to those of the 
series motor. This motor has been designated as the repulsion 
motor. Although it was expected that it would find a ready ap- 
plication in the railway field it has not come into use largely 
because of its inability to operate upon direct current systems 
and the additional fact that it apparently has no marked 
advantages over the series motor. 

^ The Alternating Current Railway Motor by C. P. Steinmetz, A. I. E. E., Vol. 
XXIII. 

Speed Torque Characteristics of the Single-phase Repulsion Motor by Walter 
I. Slichter, A. I. E. E., Vol. XXIII. 

Alternating Current Motors by McAllister. 
t6 



242 ELECTRIC RAILWAY ENGINEERING. 

Induction Motor. — The induction motor has characteristics 
similar to those of the shunt direct current motor and is, therefore, 
generally unfit for railway service. It may be designed, however, 
for several different speeds, usually by placing a winding upon 
the rotor and varying the resistance in the rotor circuit or in some 
cases by the so-called concatenation method in which the stator 
of one motor is supplied from the rotor circuit of a second motor. 
With these adaptations this motor has been considerably used 
abroad for railway service and in one installation in this country, 
upon the Great Northern Railway^ where the requirements seemed 
to be particularly well filled by a motor of constant speed charac- 
teristics. 

Frequency. — The question of frequency has not been directly 
referred to in the above discussion. If reference be made again 
to the factors which were necessarily changed in the direct current 
motor to adapt it to alternating current operation it will be noted 
that these factors, principally reactance voltages, are reduced by 
reduced frequency. The lower the frequency, therefore, the 
easier it becomes to design a satisfactory alternating current rail- 
way motor and the greater the capacity which it is possible to 
obtain with a given size and weight of frame and, therefore, the 
greater the capacity that can be supplied to a single truck or to a 
single pair of driving wheels. 

Rating. — Railway motors, because of their rather intermittent 
service at varying loads with a greater amount of ventilation in 
actual use than upon the testing floor, are rated differently than 
other electrical machinery. 

A motor is said to be of a certain capacity expressed in horse 
power if it will delvelop such a horse power continuously for i hr. 
with a temperature rise of 75° C. above the room temperature 
corrected to 25° C. when operating with the openings in the motor 
frame uncovered. This represents a rather arbitrary rating, but 
offers a basis for the comparison of motors. 

Motor Selection. — The method of determining the total power 
required to operate the car has been explained in a previous 
chapter. After the number of motors per car has been decided 

^ The Electric System of the Great Northern Railway Company at Cascade 
Tunnel by Cary T. Hutchinson, A. I. E. E., Vol. XXVIII. 



MOTORS. 243 

upon as outlined in the last chapter, the capacity of the motors 
to be installed may be approximately determined by dividing the 
average car demand expressed in horse power for the various 
runs by the number of motors per car. If care be taken not to 
load the motor continuously with its rated load and still make 
due allowance for its overload capacity for short intervals and 
the extra demands of abnormal service, this method should per- 
mit a correct selection of the nearest standard motor to be made. 

Several other methods of making this selection may be adopted, 
however, and it is always well to check the motor capacity chosen 
by two or more processes. They will be briefly explained in 
order of their ease of application. 

Selection by Comparison. — A very rough and simple method 
quite commonly used is to prepare a table from technical jour- 
nals or the railway census of the equipments of various roads 
operating under as nearly as possible the same conditions as the 
proposed road. This table should include number and capacity 
of motors, average voltage, schedule speed, weight of cars, lay- 
over at terminals, stops per mile, average grade and if possible 
the watt hours per ton mile demanded. By comparison with such 
a table the correct standard size of motor for the new equipment 
may readily be determined. 

Effective Current Method. — It is possible to obtain from 
manufacturers' test records not only the rating of the motor, but 
also its continuous current capacity at one or more average vol- 
tages, i.e., the current which may be supplied to the motor con- 
tinuously without exceeding the limit of 75° C. temperature rise. 
The temperature curves of Fig. 13 may also be obtained from 
which the time required to rise to 75° C. above the room tempera- 
ture from the start with the motor cold can be found for each 
value of current supplied to the motor, as well as the time required 
to rise 20° above 75° C. for the various possible over-load currents. 
In making use of these data it should be remembered that the 
heating of a motor is proportional to the square of the current. 
The heating value of the current or "effective" current for a 
given run is not the average ordinate of the current-time curve 
of that run, but the square root of the average squared current. 
If then the effective current for the various runs as determined 



244 



ELECTRIC RAILWAY ENGINEERING. 



from the current-time curves be compared with the continuous 
current rating of the motors with due allowance for temperature 
rise of short duration produced by overload currents as deter- 
mined from the temperature curve^ the proper motor may be 
readily selected. In short, a temperature time curve is really 
determined for the various runs and the motor so selected that 
this curve will not exceed 75° C. rise for other than short inter- 
vals of time. 




.40 60 80 100 130 140 160 180 
Commercial Rating of Motor in H.P . 

Fig. ICO. 

Method Proposed by Armstrong. — In a paper before the 
American Institute of Electrical Engineers^ Armstrong suggests 
that a series of curves such as Fig. loo, each representing the 
motor capacity required for a given weight of car per motor and 
for a certain speed, acceleration, etc., be prepared from theoret- 
ical and practical test data and used for quick approximations 
of motor capacity. Fig. loo is plotted for straight level track 
with the following assumed values: 

Gross accelerating force, 120 lbs., per ton. 

Braking decelerating force, 120 lbs. per ton. 

Duration of stops, 15 seconds. 

Duration of coasting, 10 seconds. 

^ High Speed Electric Railway Problems by A. H. Armstrong, A. I. E. E., 
Vol. XXII. 



MOTORS. 245 

Since this data does not take into consideration grades and 
curvature or other values of acceleration, deceleration, etc., than 
those listed, either a large number of such charts must be plotted 
or the results taken from same carefully corrected for any varia- 
tion of actual from assumed conditions. 

Method Proposed by Storer.^ — This method assumes that a 
certain motor has been tentatively selected and that it is desired 
to determine from test under conditions similar to those of actual 
service whether or not this particular motor will fulfill the require- 
ments. 

The effective current for the various runs is determined as 
explained above and the average voltage at the terminals of the 
motor found from the voltage time curve. If, now, the motor 
be operated with this effective current and with the average 
voltage impressed upon it, the motor lossss will be the same as in 
practice and the heating of the motor under service conditions 
may be determined therefrom. It should be remembered, how- 
ever, that the ventilation of the motor is better in service and it 
may usually be depended upon to carry from 20 to 25 per cent. 
more load with the same temperature rise when on the car. This 
allows a good factor of safety if the motor be selected from test 
results. 

Method Proposed by Hutchinson.^ — The method employed 
by Hutchinson where a large number of motor determinations 
are to be made by a manufacturing or an engineering company 
is one involving mathematical equations based upon a large 
number of general charts deduced from the typical speed time 
curves. In place of assuming the straight line speed time curve 
of Part I, Chapter X, to be correct, a mathematical correction 
applying to the difference in area between the accurate and the 
straight line speed time curve is used and constants derived which, 
when substituted in the equations given, enable the latter to be 
solved for correct motor capacity. For further details reference 
should be made to the original paper. 

^ By N. W. Storer, Street Railway Journal, 1901. 
2 A. I. E. E., Vol. XXI. 



CHAPTER IV. 
Types of Control. 

The necessity of starting a car by first impressing a low voltage 
upon its motors and then gradually increasing the voltage as the 
motors speed up until they are receiving their rated voltage, has 
been previously explained. The advisability of maintaining a 
constant current through each motor during the constant accelera- 
tion period was also pointed out. It is now necessary to consider 
the various standard control systems which have been devised 
to accomplish the above results. 

Rheostatic Control. — The earliest type of control, which is 
now practically obsolete, made use of a rheostat in series with the 
motors, but did not change the motor connections from start to 
full speed. Two complete revolutions of the controller handle 
were necessary to cut out all the resistance, but the rheostat was 
so designed that the controller handle could be left in any position 
indefinitely and correspondingly small variations of speed obtained. 

Series Parallel Control. — Practically all the control systems 
in use with direct current railway motors at the present time, al- 
though differing widely in detail, operate upon the series parallel 
principle. The two motors of a two motor equipment or those of 
each group of a four motor equipment are first connected in series 
with one another and also in series with a resistance. This resis- 
tance is then reduced by three or four steps until the two motors 
are alone in series across the circuit from trolley to ground. This 
notch of the controller is termed a "running" notch as the con- 
troller may be left in this position continuously, resulting in about 
half speed. With the next step, the motors are changed from 
series to parallel connection and a resistance again introduced. 
This resistance is reduced in the succeeding steps until upon the 
last notch all motors are in parallel without resistance. This is 
ordinarily the full speed position, although in some types of this 
control an additional step is employed which shunts the motor 

246 



TYPES OF CONTROL. 



247 



field with a resistance and thus increases the speed still further. 
A K-12 controller, which is commonly found on city cars with 
four motor equipments is shown diagrammatically with motor and 
resistance connections in Fig. loi. The connections for the 
various notches may be readily traced if the heavy black horizon- 
tal bands representing the copper sectors on the control cylinder 




Fig. ioi.— K-12 Wiring Diagram. 



be assumed to move one numbered notch to the left for each 
change of connections. Care should be taken to trace out the 
reversal of armature connections as the reverse cylinder repre- 
sented by the heavy bands at the right of the figure is turned. 
The switches numbered (19) and (15) are used in cutting out one 
set of motors in case of their failure. The resistance steps are so 



248 



ELECTRIC RAILWAY ENGINEERING. 



proportioned that if the controller is steadily "notched up" an 
approximately constant current will be maintained through each 
motor. A diagrammatic illustration of the various steps is found 
in Fig. 1 02. As may have been inferred from the above discus- 
sion, the resistances are designed to remain in the circuit for a 



Notch Resist. 1 Arm. I Fid. 2 Arm. 2 Fid. 

1 — tAaaaa/vXIVvw sQsAAA^ 



■^-aAaa/vn/^(3v\aa/ xIVvw 



■MaaAaaaXIVvw OsAaat 



■J-WVWV\3\AAA/ N^/^/^^ 



■J-AAAAWXVVVV N(IVVVV 



Transition 



^^-^MAAAAXIVwv Oww 



Transition 



^^^\VvAAA/"N(lV\AA/ ' nOvWV^ 



Transition 



^^^aMaaa/XVvw 'p>Qww 



aaaAaa^|X3aaa/ pO/vvv^ 



■AAAAAA/qNQvvAA/ pQAAAr 



AAAAAA/^X^AAA/ ' j-^QvAAAr 



Fig. 102. 



short time only and will therefore overheat if they be left in circuit 
continuously. 

The mechanical construction of the series-parallel controller 
may be noted from Fig. 103 which shows the interior of a K-ii 
controller with asbestos barrier opened. This particular con- 
troller has been provided with additional barriers by the operat- 
ing company to prevent arcing between contacts. The main 



TYPES OF CONTROL. 



249 



drum with its copper sectors insulated from the shaft and engag- 
ing copper contact fingers will be seen on the left and the reverse 
cylinder of similar design on the right with the blow-out magnet 
below. A sufficient flux is produced in this magnet to blow out 
the arc which is formed between the various fingers and sectors 
as the circuits are opened. At the bottom will be found the motor 
cut-out switches and the connection board. 

In order to prevent the current through the motors from being 
increased too rapidly two different methods are used. A mechan- 
ical device may be attached to the top of the controller which 




Fig. 103. — K-ii Controller. 



by means of a ratchet and pawl prevents the forward movement 
of the controller handle in a single swing, but requires a slight 
backward movement at each notch to disengage the pawl and 
thereby allow sufficient time for the current to decrease to its 
normal accelerating value. The second method involves the use 
of a specially designed controller with a limit relay through which 
the motor current passes. Although the handle may be thrown 
completely around in a single swing, this movement simply puts 
a coiled spring in tension which ''notches up" the controller as 
fast as the interlocking relay will permit. When the current falls 
to a predetermined value on each step the relay unlocks the con- 



250 



ELECTRIC RAILWAY ENGINEERING. 







TYPES OF CONTROL. 



251 



troller spindle and allows it to progress to the next step auto- 
matically. 

Master Control. — With the rapid increase in the current 
required by the motors as the size and capacity of electric railway 
equipment advanced, it became more and more difficult to design 
a controller of the type described above to continually break these 
large currents. As a result a master controller is often found in 
the motorman's cab, quite similar in principle to the large con- 




FiG. 105. — Contactor. 



trollers, but designed to control an auxiliary circuit only. This 
auxiliary circuit operates a series of contactors or solenoid operated 
main switches mounted under the car. With such a system the 
contactors may be sufficiently large to control the heavy currents 
safely and little room is required for equipment above the floor, 
not to mention the reduction in the amount of heavy cable de- 
manded by such an equipment. The auxiliary circuit may be a 
high resistance circuit supplied from the trolley or in some in- 
stances it is supplied by a storage battery of about 14 volts. 



252 ELECTRIC RAILWAY ENGINEERING. 

Multiple Unit Control. — There is a demand in elevated, sub- 
way and heavy interurban service for the operation of a number 
of cars in a single train from the motorman's cab of the front car. 
A marked advance in the design of control equipment was made, 
therefore, when the multiple unit control system was developed 
by Sprague. This system embodies the use of the master con- 
troller explained above not only, but it permits the contactors 
upon all cars to be operated simultaneously by the master control- 
ler of a single car, the small auxiliary circuit wires alone extending 
between cars through the agency of flexible cables and plug con- 
tacts. The equipments are all interchangeable so that any car 



Fig. 106. — Unit Switch Group. 

may be made a control car. Fig. 104 represents the wiring dia- 
gram of both the main and auxiliary circuits of the multiple unit 
control in detail, while Fig. 105 illustrates the contactor with its 
relay contacts at the bottom and its asbestos trough for the circuit 
breaker at the top. 

Unit Switch Control. — The unit switch control is a system 
developed by another manufacturing company to meet the require- 
ments of master control of single car equipment or of multiple 
unit control. In fact upon one large railway system cars with 
the unit switch control and the Sprague multiple unit control are 
operating interchangeably in the same train. 

The unit switch control differs from the Sprague multiple unit 
system principally in details of operation, the principle of the two 



TYPES OF CONTROL. 



253 



being the same. Both systems have the main switches and 
reversers located under the car, the operation of these switches 
being controlled by the master controller and an auxiliary or relay 
circuit. The unit switch system obtains its energy for the auxil- 
iary circuit from one of two 14-volt storage batteries carried on 




Fig. 107. — Unit Switch Master Controller. 



the car, while the control circuit of the multiple unit system is 
supplied from the trolley. In the former system the main switches, 
Fig. 106, are operated by air pressure obtained from the main air 
brake reservoir, the air valves being operated by the battery 
circuit. 

The automatic '^notching up" feature of the unit switch sys- 
tem, which may also be secured with the Sprague multiple unit 



254 



ELECTRIC RAILWAY ENGINEERING. 



control is accomplished by providing the main switches or con- 
tactors with relay contacts which make the proper connections 
in the auxiliary circuit as they open or close. 

The master controller of the unit switch system, Fig. 107, 
is provided with three forward and three reverse notches, the 
function of which will be more clearly seen by referring to Fig. 108, 



Line Switch q I 




Limit Coil 



Fig. 108. 



which is a much simplified connection diagram. The first notch 
closes the line switch (T) and the unit switches (a) and (b) , thus 
putting the motors in series with all resistance in circuit. This is 
not a permanent running notch, but the train maybe thus operated 
at slow speed for switching, etc., for a short time. 

The second notch on the controller is the full series running 
position. This closes switch (C) which has interlocking contacts 




E 






^ 



90 « 

Type 276 

3rd 




Type 251 CUIt Switch Qtoup 

Fig. 109.— Wiring Diagram, Unit Switch Multiple Unit Control. 



TYPES OF CONTROL. 255 

which in turn close (RRi). The latter switch carries interlocks 
which close (RJ and so on closing (RR2), (Rz)^ (RRs)? (Ra)? 
etc., in order, cutting out corresponding resistance steps until the 
motors are in series without resistance between trolley and ground. 

Notch No. 3 or the full parallel running position closes switch 
(d) which in turn breaks the auxiliary circuit of (b) and the latter 
switch opens together with all the resistance switches except (c) . 
When (b) has completely opened it causes switches (e) and (G) 
to close. When these are fully closed their interlocking relays 
open switch (d). When (d) is again open the circuits through 
the resistance switches (RRJ, (Rj), (RRs); etc., are closed con- 
secutively until the resistance has again been gradually cut out 
and the motors are finally operating in parallel across the line with 
no resistance. Limit relay switches described above prevent the 
resistance switches from closing before the current has decreased 
to its normal accelerating value. This maintains nearly constant 
current during the acceleration period. 

In some forms of this control the handle of the master controller 
is automatically returned to the "off" position if the motorman 
takes his hand from same. This is arranged not only to shut off 
the current, but also to apply the air brakes automatically. With 
this design an additional coasting notch is introduced next to the 
' -off" position for which the current is off, but the brakes are not 
applied. 

A complete wiring diagram for the unit switch automatic mul- 
tiple unit control system including both auxiliary and main cir- 
cuits will be found in Fig. 109, but because of its complication 
the simplified diagram of Fig. 108 will be found preferable for all 
but detail connections. 

It must be remembered that in all multiple unit control systems 
the power circuit of each car is complete in itself, with indepen- 
dent contacts with trolley or third rail. Each car, therefore, 
must have its own limit swatch which may be adjusted for a dif- 
ferent value of current for each car to correspond with the equip- 
ment upon that particular car. Provision is also made for all the 
switches to open on any one car in case of failure of power on that 
particular car, the switches "notching up" automatically when 
the power is again supplied. The latter feature is important with 



256 ELECTRIC RAILWAY ENGINEERING. 

third rail operation in which the power is off when passing over 
each crossing. 

Alternating Current Control. — As the principal advantage in 
the use of alternating current motors on the car is the possibility 
of using high trolley voltages and as the alternating current motors 
are best designed for low voltage, i.e., from 200 to 225 volts, a 
transformer must be used on the car to reduce the trolley voltage 
to that suitable for the motors. Since taps may be taken from 
the various coils of this auto-transformer to furnish still lower 
voltages useful in starting the car without the resistance loss en- 
tailed by the resistance type of direct current motor control the 
principle of alternating motor control differs somewhat from those 
previously explained. 

Alternating current control systems may be either hand oper- 
ated or of the master control multiple unit type. If the former, the 
controller is similar to the (K) series parallel drum controller 
with the exception that there are fewer notches, usually five or 
six only, and no series parallel connections. The magnetic blow- 
out coil is also omitted as the alternating current arc is not 
difficult to extinguish without the coil. The various contacts 
made between controller sectors and the stationary fingers serve 
to connect the motors, generally permanently connected two in 
series, to the various taps of the auto-transformer. The reversal 
of the motors is accomplished in the same manner, the reverse 
cylinder reversing either the armature or field connections. 

With the master alternating current control the principle of 
operation is the same as before. The magnetic cores of the 
reverser and contactors must, however, be laminated for use on 
alternating current circuits. 

In order that connections may be changed from one transformer 
tap to another without opening the circuit it is necessary to close 
a local circuit through a portion of the transformer winding, i.e., 
if special precautions are not taken a short circuit will be formed 
in a portion of the transformer coil as two taps of the transformers 
are connected to the same motor terminal. In order to avoid this 
difficulty the current is reduced in the local circuit by means of 
''preventive" resistance or reactance leads as in the case of the 
single-phase motor. 



TYPES OF CONTROL. 257 

The auto-transformers used with the alternating current motor 
equipments have been standardized for 3000, 6000, and 10,000 
volts trolley potential and are connected directly between trolley 
and ground, the motor leads being connected to taps near the 
grounded side of the transformer. The transformer is of the oil 
cooled type and is mounted under the floor frame of the car. 

Combined Alternating and Direct Current Control. — 
As previously pointed out it is desirable that most alternating 
current interurban roads operate cars to the heart of the terminal 
cities. They must, therefore, be able to operate upon both al- 
ternating and direct current. In order that the control equip- 
ment may be fitted for either system some changes in detail must 
be made and a considerable complication of circuits results. The 
various parts of the apparatus such as controller, reverser, con- 
tactors, etc., are used in common by the two systems. A number 
of changes in connections, however, must be made in shifting 
from one system to another. These are principally as follows 
when changing from alternating to direct current operation: 

Change transformer taps to resistance taps. 

Change main fuses or circuit breakers. 

Change lightning arresters. 

Introduce the magnetic blow out into the circuit. 

Change lighting and heating circuits. 

Reconnect fields of air compressor motor for series operation. 
In order that these changes may be made in one operation the 
cables involved are connected to a second control drum similar to 
the main controller. This is styled the "commutating switch," 
the above changes being made by a simple movement of the 
handle. This change may also be made automatically at full 
speed by providing a release for the switch when no potential is 
supplied so that it will open as the car reaches an insulated section 
in the trolley between the alternating and direct current systems. 
The switch is designed to reset automatically in the opposite direc- 
tion as the direct current trolley is reached and vice versa. 

As may be inferred from the above an added complication 

enters into the problem in operating the air compressor for the 

air brake system. In some installations a motor generator set of 

small capacity is installed to furnish 550 volts direct current when 

17 



258 ELECTRIC RAILWAY ENGINEERING. 

supplied with alternating current from the transformer. The 
standard direct current air compressor may then be used. An- 
other method more often found is to design the compressor motor 
for both alternating and direct current, connecting the field coils 
in parallel for the former supply and in series for the latter. 

Whereas the combination of the two control systems upon one 
car adds considerable complication, as will be seen from Fig. no, 
which represents the complete wiring diagram for an alternating 
current-direct current control equipment, and although the first 
cost and maintenance charges are necessarily increased thereby 
the added advantages of alternating current operation apparently 
warrant such an installation, for several roads are successfully 
operating such an equipment. 




Fig. jio.— Wiring Diagram, A-C. D-C. Control. 



CHAPTER V. 
Bbakes. 

The problem of stopping a car is quite as important as that 
of acceleration. Since the kinetic energy of the car must be over- 
come in a very few seconds the power required for braking 
the car is usually many times that required for accelerating. 
Whereas the rate of deceleration and energy required during 
the braking period have been already considered, it is now 
necessary to study the braking forces more in detail as well as the 
various types of equipment which have been designed for the 
production and control of such braking forces. 

Electric cars must be accelerated and retarded by virtue of the 
frictional force between the wheels and the rails. As this force 
is proportional to the weight on the wheels, the available force is 
conveniently found from the ratio of horizontal pull in pounds 
necessary to slide the wheels on the rails to the pressure between 
wheels and rdils. This ratio is commonly termed the coefficient 
of friction. It has been found to vary with the materials in 
contact, and the velocity and the length of time during which the 
force is applied. 

While many different devices have been tried out in practice 
for producing the necessary frictional forces to stop a car, the one 
which is now almost universally used in both electric and steam 
railroad service is the application of a brake shoe, usually of cast 
iron or a combination of cast iron and other materials, to the treads 
and flanges of the car wheels by means of either hand or air pres- 
sure transmitted through the agency of a carefully proportioned 
system of levers. 

Coefficient of Friction. — An experimental study of the coeffi- 
cient of friction between cast iron brake shoes and steel wheels 
under practical service conditions was made by Galton and 
Westinghouse in 1878, and the results of these tests, published in 
the 1879 proceedings of the Institution of Mechanical Engineers, 
which are given in the following tables have been ever since con- 

259 



26o 



ELECTRIC RAILWAY ENGINEERING. 



sidered as classic, the few later tests which have been made 
making little if any change therein. 



TABLE XXI. 

Coefficient of Friction at Various Speeds with Cast Iron Brake Shoes 

ON Steel Tires. 





Velocity 


( 


Coefficient of friction 


No. of tests from 
which mean is 


M. p. h. 


Ft. p. sec. 


Extreme 




taken 






Mean 








Max. 


Min. 




12 


60 


88 


.123 


.058 1 .074 


67 


55 


81 




136 


.060 




III 


55 


50 


73 




153 


.050 




116 


77 


45 


66 




179 


.080 




127 


70 


40 


59 




194 


.088 




140 


80 


35 


51 




197 


.087 1 


142 


94 


30 


44 




196 


.098 


164 


70 


25 


36.5 




205 


.108 


166 


69 


20 29 




240 


•133 1 


192 


78 


15 


22 




280 


•131 




223 


54 


10 


14 -5 




281 


.161 




242 


28 


7-5 


II 




325 


.123 




244 


20 


Under 5 


Under 7 




340 


.156 1 


273 




Just moving . . . 


Just moving . 










33° 













TABLE XXII. 

Effect of Elapsed Time on Coefficient of Friction. 



Speed 


Coefficient of Friction 


M. p. h. 


Start 


After 5 sec. 


1 

j 

After 10 sec. After 15 sec. 


After 20 sec. 


20 

27 

37 
47 
60 


.182 
.171 
.152 
.132 
.072 


.152 
.130 
.096 
.080 
.063 


■^33 
.119 
.083 
.070 
.058 


.116 

.081 
.069 


.099 
.072 















BRAKES. 261 

From the above tables the maximum pressure to be applied 
to the brake shoes may be determined under the various service 
conditions in order to provide the required frictional tangential 
force. To determine what the limits of the latter are the coeffi- 
cient of friction between wheels and rail must be known. This 
value varies widely with the condition of the rail, but may be 
safely assumed from 0.15 to 0.30 when the rail is wet and dry 
respectively. These latter values are coefficients of static friction 
which are greater than dynamic friction if other conditions are the 
same. For if the wheels are rolling, there is no relative sliding 
between wheels and rails and the frictional force to be considered 
is that necessary to start one body from rest upon the other and 
not that lesser force necessary to keep one body in motion upon 
the other. The maximum limit of brake shoe friction is now at 
once apparent, for it must not exceed the static friction between 
wheels and track. If it were to exceed that value the brake 
shoes would ''lock the wheels" and the latter would "skid" on 
the rails with increased instead of lessened speed because of the 
lower value of dynamic friction thus suddenly brought into 
play between wheels and track. 

Theoretically, cars should be equipped with braking apparatus 
which will be able to approximate as nearly as possible this maxi- 
mum value for emergency stops, but since the braking force with 
hand brake e(q[uipment depends upon the strength of the motor- 
man and with air brake equipment upon the variable air pressure, 
it is usually possible to "skid the wheels" on the average car if 
the brakes are applied too forcibly. Further, since Table XXI 
shows that the friction between brake shoe and wheel increases 
as the speed decreases during the braking period, a force applied 
to the brake shoes when braking is commenced which is slightly 
less than that necessary to lock the wheels may become suffi- 
ciently great to produce that result at lower speeds for the reason 
that the static friction between wheels and track remains constant. 
Every experienced motorman understands the results of such an 
application of biakes and releases and reapplies the braking pres- 
sure with less and less intensity as the car comes to a stop. Fail- 
ure to do this results in too sudden a stop for comfort, a severe 



262 



ELECTRIC RAILWAY ENGINEERING. 



chattering of the brake rigging and possible skidding, and in- 
cidentally marks an inexperienced or careless motorman. 

Another factor which must be taken into consideration in 
stopping a car comfortably and safely is the condition of the track, 
the sudden and unexpected skidding of wheels and the conse- 
quent sudden increase in speed having been the cause of many an 
accident. It is a peculiar fact that with a very thin film of water 
on the rail due to a slight shower, the friction is greatly reduced 
over that of a dry rail or even a thoroughly wet rail. Again the 
crushing of leaves or weeds on the tread of the rail or too generous 
a supply of track grease often make it impossible to stop on a 
section of track thus affected without the use of sand. Cars 




Fig. III. 



have been known to slide down long hills with tracks thus covered 
while the motorman was utterly powerless to reduce the speed, 
even with the reversal of the motors. Most roads, therefore, 
provide a generous supply of sand on each car not only, but 
require the track repair crew to keep the track free from leaves, 
grass and weeds. 

Braking Forces. — If the car is to be stopped by the appli- 
cation of pressure to the brake shoes bearing upon the car wheels 
as is ordinarily the case, it will be noted at once that the forces 
tending to move the car forward and those applied as resistances 



BRAKES. 



263 



to stop the motion do not lie in the same horizontal plane, the 
former acting at the center of gravity of the combined loaded car 
body and trucks and the latter at the contact between wheels 
and rails. The result is easily seen to be a tendency to raise the 
rear of the car from the track, the forces acting at the center of 
gravity of the car having a moment about the front truck. In 
addition, t lere is a tendency for the rear wheels of each truck to 
lift from the track for the reason that the forces at the king pin 
and center of gravity of the truck have a moment about the front 
wheels. The resulting effect is that the pressure is lessened 
between car and rails at the rear and the static friction depended 
upon for braking thereby reduced. Either the braking pressure 




Fig. 112. 



must be reduced upon the rear truck over that of the front truck 
and that of the rear wheels of each truck over that of its front 
wheels or else all braking pressures must be lowered considerably 
below that possible at the front end of the car. That the braking 
pressures on the rear truck cannot be made less than those of the 
front truck by any change in the leverages on the car in the case 
of double-end cars is obvious. With single-end interurban cars 
such provision is often made. There is, however, a method of 
hanging brake shoes with the supporting link of the brake shoe out 
of line with the tangent to the wheel at the center of the shoe 



264 



ELECTRIC RAILWAY ENGINEERING. 



which will vary the pressure between shoe and wheel with the 
direction of operation of the car. This may be^ illustrated by 
referring to Fig. in where the brake shoe hanger is 5° out of line 
with the tangent. With the car moving toward the right the 
frictional force at the shoe is balanced by a force of compression 
in the hanger plus a force normal to the car wheel proportional 
to the sine of 5°. This is added directly to the brake shoe pres- 
sure. If the car be operating toward the left, thus making the 
wheel shown in the figure the rear wheel of the truck, the frictional 
force produces a tension in the brake shoe hanger and a force 
proportional to the sine of 5° tending to reduce the pressure ex- 
erted by the brake rigging. Whereas this effect may be increased 
by increasing the angle between brake shoe hanger and tangent, 
too great an increase of this angle tends to bind the shoes upon 



Direction of Motion 







Fig. ii^. 



the wheel as in the case of a toggle joint causing chattering of the 
brake rigging and fiat' wheels. Such a condition often found on 
car trucks is Illustrated in Fig. 112, where the angle has been 
increased to 30°. 

In order to determine the concrete value of the resultant 
weight upon each wheel of a car, it is necessary to analyse all the 
forces acting thereon as outlined in Fig. 113 and to balance the 
moments of the forces about any single point as in any problem 
in mechanics. A sufficient number of equations will result to 
permit the weights (WJ, (W^), (W3) and (WJ to be calculated 
and the corresponding frictional forces (FJ, {F^, (F3), and (F^) 
determined through the agency of the coefficient of friction. In 
determining the above equations, it must be remembered that 



BRAKES. 



265 



the rotative inertia of the car wheels, axles, and motor armatures 
must be overcome in stopping the car as well as the translational 
inertia of car and trucks. 

Whereas, the method above outlined will result in a very ac- 
curate analysis of the various weights and forces involved, it 
would be seldom indeed, that the electrical engineer would make 
such a calculation before writing specifications for car equipment. 
The effect of reduction of pressure at the rear of the car may be 
taken roughly at 1 5 per cent, and the brake rigging designed for a 
resultant brake shoe pressure corresponding to 85 per cent, of 
the actual static weight on wheels. 

Braking Equipment. — It has been previously stated that the 



Pieced Point 




Brake Cylinder 



Fig. 114. 



hand and air brake systems are now almost universally used in 
electric railway service. The former is used alone upon small 
city cars, while both systems are universally applied to the heavier 
suburban and interurban equipment. Where both are used the 
same brake rigging is installed for both, the leverages in the case 
of the hand brake being greater to make up for the relatively 
small pull the motorman can exert as compared with the air 
pressure of the brake cylinder. A typical brake rigging installa- 
tion may be seen in Fig. 114, the operation of which will be self- 
explanatory if it be stated that the piston of the air brake cylinder 
is forced forward by air pressure, when the proper valve position 
is provided by the motorman, just as the piston of a steam engine 
is operated. The principal dimensions of the various parts of 
the equipment of several interurban cars of the Middle West are 
given in Table XXIII, all of which refer to Fig. 114. The ratio 
between brake shoe pressure and brake cylinder pressure may be 



266 



ELECTRIC RAILWAY ENGINEERING. 



readily obtained from the following equations. With this ratio 
known the air brake pressure per square inch of piston area may 
be quickly determined for various desired brake shoe applications. 



TABLE XXIII. 
Dimensions of air Brake Equipment. 



Interurban 


Dimensions of levers in inches 


car 


A 


B 


C 


D 


E 


F 


G 


I 

2 

3 
4 


10.5 

9-5 
12.0 
II .0 


9:0 

9.5 
23.0 
17.0 


35 


7.0 
6.0 
5-0 


16.0 
18.0 
16.0 
12.5 


4.0 

7.0 

S-o 


13.0 
18.0 

15-0 
12.5 



Let (P) represent the total force on the piston of the brake 
cylinder and designate the resultant forces in the various links 
by the letters appearing upon the links in Fig. 114. 

P = Air pressure X area piston. (103) 

From the ratios of lever arms the following equations may be 
derived : 

WPA 

2 ~2B 

Y(D + E) 



Y 



T = 



D 



(104) 
(105) 



V = 



YE 



T' = 



D 

V(F + G) 



(106) 
(107) 



G 



If the ratio between total pressure exerted by all brake shoes 
to brake cylinder pressure be signified by (R). 

4(T + TO 



R (for a double-truck car) 



(108) 



Substitution in the above equations of values for the four cars 



BRAKES. 



267 



in Table XXIII results in the forces listed in Table XXIV with 
a 10 in. cylinder and maximum air pressure of 70 lb. per sq. in. 



TABLE XXIV. 
Forces Acting in Air Brake Equipment. 









Forms in 


pounds 








Interurban 
















car 


















P 


W 


Y 


T 


V 


T' 


R 


I 


5.497 1 


6,400 


3,200 


13,450 


10,250 


13,400 


19.6 


2 


5,497 


5,497 


2,748 


9,830 


7,080 


9,830 


14.4 


3 


5,497 


2,860 


1,430 


5,250 


3,820 


5,100 


7-54 


4 


5,497 


3,550 


1,775 


6,210 


4,430 


6,210 


9.06 



From the above table it will be seen that the multiplying power 
of the brake levers on four interurban cars taken at random 
varies from 7.5 to 19.5. 

It should not be forgotten that the above forces are based upon 
an emergency application of air of 70 lb. pressure which is seldom 
used. For an ordinary service application the forces would 
average less than one-half the above values. 

A further calculation may be made from Table XXIII which 
is of value in determining the adequacy of the equipment for the 
service. Car No. 4 in this table weighs in the neighborhood of 
25 tons. The total brake shoe pressure exerted on all wheels 
with a 70 lb. application of air is 

8 X 6,210 = 49,680 lb. 

Ratio of total brake shoe pressure to weight of car is 99 . 2 per cent. 
If the coefficient of friction were the same between shoe and wheels 
that it is between wheels and rails it would be possible to skid 
the wheels with an application of air slightly above 70 lb. 

Brake Rigging. — The levers by means of which the braking 
force is transmitted from hand brake or brake cylinder to brake 
shoes are of heavy strap iron linked together with steel pins 
provided with cotter pins and supported from the under frame of 
the car by means of strap iron stirrups. Links in tension are 



268 



ELECTRIC RAILWAY ENGINEERING. 



usually constructed of i in. round iron rod. The circle bar 
between links (Y) and (W) Fig. 114 is provided with the truck 
together with a clevis which may be welded to rod (W) and 
which is so designed as to slide on the circle bar as the trucks 
swing with respect to the car body when turning a curve. 

The hand brake consists of the familiar vertical ratchet crank 




Fig. 115. — Straight Air Brake Equipment. 



or wheel in the motorman's cab which winds up a chain under 
the car vestibule, this chain exerting a tensile force at H, Fig. 114. 
Straight Air Brake Equipment. — The air brake equipment 
in its simplest form consists of a motor driven air compressor, a 
storage reservoir, a brake cylinder, a governor, two engineer's 
valves with gauges for double end equipment, a system of levers, 



BRAKES. 269 

complete piping equipment and usually one or more air whistles 
to act as signals. Fig. 115 represents the apparatus above out- 
lined. The compressor, reservoir, brake cylinder and piping are 
supported from the under frame of the car. The governor is 
often placed on the car floor under one of the end seats, while the 
remainder of the equipment is in the motorman's cab. 

The air compressor is a direct connected pump and direct 
current 550 volt series motor connected between trolley and 
ground with only a snap switch, the governor switch and a fuse 
in circuit. The trolley connection is made between circuit 
breaker and trolley so that the compressor will not stop when 
the circuit breaker opens. 

The governor is a pneumatically operated switch which can be 
adjusted to close the compressor circuit and thereby start the 
compressor when the air pressure falls below a predetermined 
value and which will automatically stop the compressor when the 
pressure reaches the maximum value desired. While there is a 
considerable range for which the governor may be adjusted, it 
is generally set to operate at about 70 and 90 lb. per sq. in. 
respectively. 

The motorman's valve is of the three position type. The 
operating handle, when moved to the "service" position opens 
the valve between reservoir and brake cylinder and applies the 
brakes. The extent to which the handle is moved in this direction 
and the time during which it is left there determine the pressure 
applied to the brake shoes. If it be desired to retain this pressure 
in the brake cylinder the handle may be moved to the "lap" 
position where all valves are closed. The handle may be re- 
moved only when in this position. By throwing the handle to 
the position opposite to that of "service" into the "exhaust" 
notch the air in the brake cylinder escapes to the atmosphere 
and the brakes are released. It is a rather unfortunate fact 
that two types of air brake valves apply the air with opposite 
movements of the valve handle. This is rather confusing to 
motormen accustomed to one method when changing to another 
road using the other system. 

Automatic Air Brake Equipment. — Contrasted with the 
above " straight air brake equipment" which is applicable to single 



270 ELECTRIC RAILWAY ENGINEERING. 

cars only, the "automatic air brake equipment" similar to that 
found on steam trains is often found on electric lines, especially 
in elevated, subway, and heavy interurban service where two or 
more cars are coupled together. The principal difference be- 
tween this system and the one previously described is the addition 
of a second or auxiliary storage reservoir and the use of a "triple 
valve." A "train line" or continuous pipe under air pressure is 
provided throughout the train, rubber hose couplings with pat- 
ented air tight knuckle joints permitting the ready closing of the 
line when shifting cars. The "triple valve," which is the vital 
part of the entire system, consists of a piston valve ordinarily 
balanced in a mid position by the auxiliary reservoir pressure 
on one side and the "train line" pressure on the other. When 
the motorman's valve is in the "service" position the train line 
is momentarily opened to the atmosphere and its pressure re- 
duced sufficiently to cause the auxiliary reservoir pressure to move 
the triple valve piston to such a position as to admit air from the 
auxiliary reservoir to the brake cylinder and apply the brakes. 
This occurs on every car of the train. To release the brakes 
the motorman's valve in the "exhaust" position allows air to 
flow from the main reservoir to the train line and raise its pressure 
so that the triple valve is again balanced and the brake cylinder 
opened to the atmosphere. One of the most valuable features 
about this equipment is the fact that any leakage or breaking 
apart of cars, etc., which will reduce the pressure in the train line 
will set the brakes upon all cars of the train. 

Quick Action Automatic System. — The automatic air brake 
as above described is applicable to trains up to about five cars in 
length. For the longer trains, however, the reduction in train 
line pressure requires an appreciable time to be felt throughout 
the length of the train. The resulting effect of some cars of the 
train braked with others free causes severe strains on the draft 
rigging, not to mention inconvenience to passengers. The " quick 
action automatic air brake system" is therefore applied to the 
longer trains. This is similar to the other with the exception 
that the "triple valve" is so designed as to feed both auxiliary 
reservoir and train line pressure into the brake cylinder. This 
procedure not only causes each car to aid in quickly reducing 



BRAKES. 271 

the train line pressure throughout the train, but it decreases the 
drop in train line pressure which must be produced at the head 
car. In other words the action is cumulative throughout the 
length of the train. 

In both the automatic systems the motorman is provided with 
a duplex gauge indicating both train line and main reservoir 
pressure. In the straight air brake system either a single gauge 
hand is provided to denote the reservoir pressure or two indica- 
tions are given, one above outlined and in addition a second hand 
to show the pressure applied to the brake cylinder. 

Friction Disc, Electric and Track Brakes. — Many types of 
special braking devices have been invented and tried out, involv- 
ing friction discs bearing upon the planed inside surfaces of car 
wheels, magnetic brakes supplied with energy either from the 
trolley or the car motors used as generators, and track brakes 
consisting of shoes bearing upon the rail instead of the car wheels 
and often designed to grip the head of the rail with a variable 
pressure. While some of these devices have served admirably 
in special instances, especially as an additional safety device upon 
severe grades, they are not in sufficiently general use to warrant 
detailed description. 

Reversal of Motors. — A method of stopping cars in cases of 
emergency, known as "reversing" consists in throwing the re- 
verse lever to the reverse position and applying power to the 
extent of one or possibly two series notches of the controller. 
This, of course, tends to operate the car in the reverse direction 
and not only stops the car with a sudden jolt but is likely to damage 
the car equipment. It is therefore seldom resorted to, but in 
case of failure of the brake rigging or to avoid a collision, it is 
sometimes a valuable protection. 

Motors used as Generators. — As a last resort, with no power 
supplied to the car, and with brake rigging damaged, there is 
yet another method of stopping the car. The reverse lever may 
be thrown into the reverse position and the controller handle 
swung into one of the parallel notches. The resulting connection 
causes one motor to operate as a generator, driven by the inertia 
of the car, thus supplying the other motor with power tending 
to operate the car in the reverse direction. This method may. 



272 



ELECTRIC RAILWAY ENGINEERING. 



of course, be used if the power supply be, present by throwing the 
circuit breaker to the open position. 

With either of the above methods involving the use of electric 
power in stopping the car, great care must be taken not to skid 
the wheels as this condition prevents a prompt stop not only, but 
is likely to flatten the wheels as well. 

Brake Tests. — It is often of great value to know the time and 




8 10 

Seconds 
Fig. 116. 



distance required in which to stop cars of various weights operat- 
ing at different speeds. This is particularly true in case of 
accidents and court litigation. Whereas these facts may be 
predetermined mathematically as has been previously pointed 
out, the actual test of a car in service is often required as well. 



BRAKES. 



273 



In order to carry out such a test thoroughly, it is necessary to 
provide a method of determining speed of car, time between 
brake signal and stop and distance travelled during this period. 
It is also well in some cases to know the air brake pressure, the 
amount of wheel skidding and the motor current in case either of 
the reverse methods are used. 



a> 
40 



35 



30 



w 

10 ( 



0) 

3 

m 

m 

60 



25 50 5 



20 


40 


4 


15 


30 


3 


10 


20 


2 


5 


10 


1 



^ 
















1 


^ 




EMERGENCY STOP 

FROM 

FULL SERIES POSITION 










\sp 


eed 




















I 


_y 




) Dista 


ace 












V 




b 












> 




/ 


N 


































I / 










) Decel 


Bi-atior 


I 




/ 


/ 






^ 




)Air P 


ressur 


9 




b 


' 


y 


^ 


jT 












/. 


X 


^ 

















3 4 5 

Seconds 

Fig. 117. 



One of the most satisfactory methods of determining the speed 
at any instant is by means of a magneto generator, driven from 
the car axle, the voltage of the generator read from a voltmeter 
in circuit being directly proportional to speed. 

The distance travelled during the braking period may be 
roughly determined from the revolutions of the car wheel or a 
similar wheel driven from the car axle, which may be caused to 
make electrical contacts every revolution. If any skidding 
occurs, this method becomes valueless. A method which has 



274 



ELECTRIC RAILWAY ENGINEERING. 



worked admirably in recent tests at Purdue University is to give 
the braking signal by means of a revolver from which a ball is 
shot beside the track, thus marking the start of the braking test 
very accurately. The distance required to stop may then be 
measured along the track from this point with a steel tape. 



*3 q 

;r, o 



3 ^ 
130 



^110 
100100 

w 

90 90 ?^' 

(^ 

80 80 16 

70 70 14 

60 60 13 

50 50 10 

,40 40 8 

30 30 6 

30 30 4 

10 10 2 























/\ 


i 


GENERATED MOTORS 

FROM 

FULL PARALLEL POSITION 






/ 


\ 








\ 




f\ 


r\ 


) Current per Moto 


. 






\ 


V, 


j 




\ 










\, 










\' 


) Acti 


ial Dis 


;aQce 




\ 


k 




















^; 


ks. 


leed 


















\ 

C 


\ 




















y^ 




. ■^ 


)Dista 


ace 










J 


/ 


\ 














y. 


V 




__\ 


\ 


) Dece! 


eratioi 


1 




J 


r^ 








\ 








J 



01334567 

Seconds 

Fig. ii8. 

All of the data of the test may readily be arranged for an auto- 
matic graphical record upon a single paper chart, thus illustrating 
clearly the desired values at any given instant. 

The results of such tests are best shown by curves similar to 
those of Figs. ii6, 117, and 118 which represent braking^tests 
made with the Purdue University Test Car^ of approximately 

^ Thesis, Purdue University, 191 1, by Luhrman, Blaschke and McLean. 



BRAKES. 275 

25 tons weight equipped with brake rigging designated as car 
No. 4 in Table XXIII. While it is believed that these figures 
are in general self-explanatory, especial attention should be 
called to the amount of skidding which took place in the stop by 
means of generated motors, Fig. 118, and also to the fact that 
the speed-time curve is seldom a straight line as is assumed in 
theoretical calculations. The error in such an assumption, how- 
ever, is obviously small. 

The results of all the tests made upon the above car are given 
in some detail in Table XXV and may prove of some value in 
approximating possible stopping time and distance under other 
conditions. 



276 



ELECTRIC RAILWAY ENGINEERING. 



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CHAPTER VI. 
Car House Design. 

As the modern car house not only provides storage for the 
rolling stock, but also furnishes room for inspection and repairs 
and often includes the shops and offices of the railway company, 
much thought must be given to its location and design. 

Location. — Too often a lot for a car house is secured before 
the size or requirements of the latter are determined, thus re- 
quiring that the car house and track layout be fitted to the lot. 
This procedure results in a limited and unsatisfactory design. 
A site of sufficient size for all the above functions of the car house, 
with proper consideration for future growth, should be selected 
in the most convenient section of the city, from an operating 
standpoint. Care must be taken to make sure that all necessary 
track privileges may be obtained from the city authorities before 
the site is finally purchased. 

In the case of the interurban car house, a location for the latter, 
together with the shops, offices and often the power house or 
substation is selected at about the middle of the line, although 
where the interurban road is operated by the company controlling 
the traction systems of the terminal cities the cars may be handled 
by the city car houses. This plan often offers the advantages of 
lessened fire risk, smaller dead mileage of cars, improved freight 
and express accommodations and better or more congenial homes 
for employees. For the advantages to be gained by locating near 
the power house, as well as for an outline of many considerations 
to be taken into account in deciding upon the proper location, 
reference should be made to Chapter V of Part II. 

The fire risk of a car house is great and abundant water supply 
and other fire protection should be available not only, but care 
should be taken to avoid all fire risk from adjoining buildings. 
The sub soil should be examined with a view toward determining 
the foundations and piling necessary, although with the lighter 

277 



278 ELECTRIC RAILWAY ENGINEERING. 

and more equally distributed weight of the car house this is not 
such a vital factor as with the power station. Good drainage 
and suitable sewer connections should, however, be available or 
easily provided. 

Layout of Tracks. — One of the first questions to be decided 
is the percentage of total cars owned for which cover shall be 
provided. This is a question upon which railway managers 
differ widely. At the 1907 Convention of the American Street 
and Interurban Railway Association a committee appointed to 
investigate this question assumed the case of a car house accom- 
modating 84 cars under cover as compared with a similar design 
capable of housing but one-third this number. The estimated 
costs were $105,000 and $45,000 respectively. With fixed charges 
at 12 per cent., this represents an annual saving of $7,200 or $85 
per car. A study of the requirements of this road showed that 
all cars not in service between 6 a.m. and midnight could be housed 
by the small structure and of course this would involve different 
cars on different days. The larger car house and the increased 
annual outlay includes simply the ability to house two-thirds 
more cars from midnight until 6 a.m. Since the $85 per car will 
nearly provide for repainting and varnishing a car each year 
and as the added deterioration of the car during this period of 
day when out of service is not great, this particular case seems to 
favor open storage. Opposed to this evidence probably the most 
important argument for complete car storage is the fact that the 
equipment will certainly receive better attention from inspectors 
and repair crew if all cars are stored within the car house, especi- 
ally in bad weather. 

The next question of importance is whether a single or double- 
end house is desired. The latter type provides more ready 
movement of cars through the house and aids greatly in clearing 
the house in case of fire. Where a whole block or two inter- 
secting streets are available it is often customary to form an 
operating loop through the car house for the cars when in regular 
service with regular inspections as they stop over the inspection 
pits. A rather complicated example of this construction is 
shown in the plan view of Fig. 119, representing the new Park 
Terminal car house in Baltimore. The principal objections to 



CAR HOUSE DESIGN. 



279 



the double-end arrangement are the difficulty in keeping tracks 
clear for thi-ough operation, the large amount of special track 
work required and the added difficulty in heating. 

Whichever of the above designs is decided upon, depending 
largely upon local conditions, the problem remains to so connect 
the various tracks of the car house with those of the main line 
that the greatest possible flexibility of car movements within the 
yard may be had without interference with main line traffic and 
without obstructing the main track with more special work than 




Fig. 119. 



is absolutely necessary. Figs. 120 and 121 illustrate several 
typical methods of solution for this problem. Case (A) introduces 
several switches into one of the main tracks, but makes no con- 
nection with the second main track. A more flexible arrange- 
ment is shown in Case (B) where a cross-over is provided to the 
second main track in addition to one located in the car house. 
The latter is often found very useful, but its installation depends 
very much upon the availability of the special work in front of the 
car house for switching purposes. If the special work in the 
main line be objected to, Case (C) may offer a satisfactoiy solu- 



28o 



ELECTRIC RAILWAY ENGINEERING. 



tion, requiring necessarily more yard room. The design of Case 
(D) uses an extra or "gauntlet" track in the street for switching, 
while (E) is similar to (B) with the exception that the operating 
tracks are on the right of the storage house. If space will permit, 
(F) Fig. 12 2, offers an ideal arrangement, allowing the through 
cars to pass through the car house for inspection or minor repairs 




Fig. 1 20. 



if desired and relieving the main line of all special work. It may 
also be used as a " Y" for turning cars which must operate single- 
ended. Designs (G) and (J) have been termed "bottle" en- 
trances involving the special work within the car house because 
of building conditions. (H) may be used often in interurban 
service where land is cheap and the car house may be placed at 



CAR HOUSE DESIGN. 



281 



some distance from the main track. Case (I) involves the use 
of the third track in the street and therefore is Kmited to use 
with wide streets only. 

The special work required for any of the above entrances 
should be of girder rail with manganese hardened centers 
regardless of the type of rail used in the street and car house. 




Fig. 121. 



This is especially true in cases in which the regular street traffic 
must pass over the switches and frogs as well as the cars entering 
the car house. 

Transfer Table. — The use of a transfer table in the car house 
often does away with much of the special work. This transfer 
table consists of a large truck operating upon a pair of depressed 



282 



ELECTRIC RAILWAY ENGINEERING. 



rails laid across the car house with its upper surface flush with 
the floor and bearing sections of rail matching those of storage 
house and outgoing tracks. A car may be run on this table in 
either direction, be transported transversely of the car house and 
run off on another track. The table may be operated by hand in 
small installations, but is ordinarily driven by an electric motor. 
A typical installation may be seen in Fig. 122. Although the 
transfer table may be found in many city car houses, it is seri- 
ously objected to by many because of the time required to shift 
cars, especially in case of fire, and the space taken up thereby, 




Fig. 122. 



which might otherwise be available for storage. To obviate these 
objections the "flush" transfer table is used to some extent, the 
cars being run up to the table on a slight gradient, the table 
trucks operating on a transverse track flush with the floor. 

Building Design. — With the above questions determined the 
design of a suitable building for a car house is a relatively simple 
matter. The two factors to be kept constantly in mind are ease 
of handling and repairing cars and fire protection. 

Fire Protection. — Car houses are recognized to be consider- 
able of a fire risk and many serious fires have consumed many 



CAR HOUSE DESIGN. 283 

thousand dollars' worth of rolling stock in a surprisingly short 
time, the entire duration of several such fires being barely 
more than 30 minutes. In many instances where there is a 
spacious yard room outside, the house rails are stoped toward the 
entrance so that the cars will coast out of the barn if brakes 
are released. In other cases many cars have been saved in case 
of fire by throwing the controller handle to the first notch and 
allowing them to run out without attendance. 

Not more than three tracks should be enclosed without a fire- 
proof partition and a single fire-proof section should not contain 
more than $200,000 worth of rolling stock as stipulated by the 
Fire Underwriters. The best design is either brick walls with 
heavy mill type roof construction of fire-proofed timber or rein 
forced concrete throughout. For the latter construction see Fig. 
122. Steel truss roof construction has proven very dangerous 
in cases of fire as the roof falls in very quickly, thus cutting off 
all possibility of getting out the remaining cars. Curtain walls 
of cement plaster on wire lath are often installed in long houses, 
separating the storage space into several fire-proof compartments. 
The front of the house and these curtain walls are provided with 
steel rolling doors. Opinion is divided regarding the advantages 
of timber roof trusses over posts for roof supports. The latter 
of course obstiuct the working area somewhat, but are often used 
to advantage for lighting outlets, sprinklers and the convenient 
support of fire fighting equipment. Automatic sprinkler systems 
are now being rapidly installed on ceilings and in aisles between 
cars for additional and prompt fire protection. These are sup- 
plied with sufficient head of water either from the city high pres- 
sure system or from a tank especially installed upon the premises. 
The appearance and relative dimensions of a typical car house 
elevation may be noted in Fig. 123. 

Pit Construction. — For convenience in inspection and repair, 
from 30 to 50 per cent, of the tracks in the car house are pit tracks, 
i.e., the floor between the rails is depressed several feet and 
cemented as shown in Fig. 123 in order that the under portion 
of the car may be accessible. It has also been found convenient 
to depress a portion of the floor between adjacent tracks by one 
or two feet for convenience in packing journal boxes, etc. 



284 



ELECTRIC RAILWAY ENGINEERING. 



Heating. — Car houses are heated principally by either steam 
or hot water, coiled pipes being located in pits and upon the 
lower portion of all walls. The boiler room, if not in a separate 
building, must be carefully protected by fire-proof walls. The 
heating of car houses is at best, an unsatisfactor}' problem, 
especially in cases where the end doors must be continually open 
for the operation of cars. 

Floors. — The floors in small storage car houses are sometimes 
of gravel fill. This is not to be approved, however, on account 
of the impossibility of keeping such a floor in a sanitary condition. 
Heavy timber flooring is probably most often found, but it should 



Tari Gra\Bl 
Rjofingon B^ok Tile 




Fig. 123. 



be avoided if the expense of concrete with cement finish can be 
seriously considered. Often the latter can be constructed with 
cinders from the power station without great expense and will 
prove the most satisfactory of all car house floors. Since sub- 
stantial piers must be laid for the track foundations in whichever 
form it may take, the floor is generally supported therefrom. 

Lighting. — Incandescent lighting by means of five light series 
groups of lamps connected between trolley and ground is often 
used in smaller installations, but a low voltage ungrounded supply 
is much preferable. Lights spaced every car length in aisles 
are usually sufficient for general illumination if generous provision 
be made for pit lighting and outlets for portable lamps. Pit 
lighting particularly should be in conduit as illustrated in Fig. 
124. General illumination for very large areas and for storage 



CAR HOUSE DESIGN. 



285 



yards may be furnished by means of arc lamps, but these are not 
popular for car house installation. 

Offices and Employee's Quarters. — The arrangement of 
offices, employee's quarters and storage for raw materials and 
tools are dependent upon local requirements and will not be dis- 
cussed in detail. The portion of the building containing the 
offices and employee's quarters is often of two stories and, where 
within the city limits, is designed to present a good architectural 
appearance. Many companies fit up spacious apartments for 




Fig. 124. 



the use of employees rather elaborately with recreation and 
reading rooms, sleeping quarters, baths, etc. Provision should at 
least be made however for making out reports and for comfortably 
spending spare time between "reliefs." An average plan may be 
seen in Fig. 125. 

Repair Shops. — It is necessary to decide at first what the 
policy of the company is to be with regard to car repair and re- 
construction. If a large interurban company is to make all re- 
pairs, reconstruct damaged cars and possibly build new cars, a 
very elaborate series of forge, wood working, machine and paint 
shops will be necessary. The majority of the smaller companies, 



286 



ELECTRIC RAILWAY ENGINEERING. 



however, make only minor repairs, often sending away wheels 
for replacement or returning rather than install the lathes and 
hydraulic presses necessary for this work. Whereas the dis- 
cussion of the former type of shop is beyond the scope of this 
treatise, especially as comparatively few of the roads are thus 
equipped, the following average list may be of value in planning 
the equipment for a small shop. The machines are listed approxi- 



^^ Man 'Hole 

3rd Ave. & lUth St. 




Fig. 125. 



mately in the order in which they would be added with increased 
demands upon the repair shops. 

I Screw-cutting lathe, 14 in. swing. 

I Vertical drill press, 24 in. 

1 Tool grinding wheel. 

4 Armature stands for rewinding armatures. 

2 Forges. 



CAR HOUSE DESIGN. 287 

I Automatic power hack saw. 

I Oven for baking insulation. 

I Commutator slotting device. 

I Wheel turning lathe. 

I Hydraulic wheel press. 

Whereas the small repair shop as well as the paint shop often 
occupy sections of the main car house, the large shops are housed 
in separate but adjacent buildings. Such an arrangement, 
showing typical floor plan details, will be found in Fig. 125. . 



CHAPTER VII. 
Electric Locomotives. 

With the recent rapid advance in electric traction there has 
come the successful design, construction, and operation of several 
types of electric locomotives. While the Baltimore and Ohio 
Railroad had previously operated electric locomotives in its 
tunnels for several years, the great impetus in electric locomotive 
development came in 1903 as a result of the requirement that 
the tunnels entering New York city be electrified. This was done 
largely as a safety precaution soon after a serious wreck in one 
of these tunnels due to the inability to read signals on account of 
the smoke inclosed in the tunnel. Likewise with the Cascade 
Tunnel of the Great Northern Railroad in Washington, experi- 
ence with a train which parted in attempting to mount the severe 
grade of the tunnel with two steam locomotives, resulting in a 
delay of the train in the tunnel and the consequent overcoming, 
by poisonous gases and smoke, of the train crew and many 
passengers, led to the recent equipment of this section of the road 
with electric locomotives. 

With the multiple unit control of motor cars, which has been 
previously described, developed to such an extent that long 
heavy trains of both motor cars and trailers are being operated 
successfully in elevated, subway and interuban service, offering a 
very flexible distribution of motive power and weight on driving 
wheels throughout the train, it might be expected that this method 
of propulsion would be applied to the heavier electrification of 
steam roads. As the traffic demands and the number of cars in- 
creased, motor and trail cars could then be added in the proper 
proportion so as to leave little excess capacity to operate at low 
efficiency as must often be the case with but one or two capacities 
of locomotives used for trains of widely varying weights and re- 
quirements. 

In spite of these advantages of the motor car, the locomotive 

288 



ELECTRIC LOCOMOTIVES. 289 

is still found to be necessary in heavy trunk line service. Its 
advantages listed below can be made to overcome those of the 
motor car by dividing the service into three or four classes such 
as switching, suburban, express, passenger and heavy freight 
and designing different locomotives if necessary for two or more 
of these types of service, thus keeping the locomotive loaded 
approximately to its rated capacity. The advantages of the 
locomotive in heavy service may be listed as follows : 

1. It eliminates necessity of re-equipping present cars as motor 
cars. 

2. It eliminates necessity of wiring some of the present cars 
with train cables for use as electric trailers. 

3. Ease in making up trains regardless of whether they have 
been electrically equipped or not — i.e., the electric locomotive 
makes use of present cars without change therein. 

4. Not necessary to make up trains in certain order with proper 
number and location of motor cars therein. 

5. Ease in reaching parts in locomotive for repair. 

6. Make up of train not affected by failure of electrical equip- 
ment. Locomotive only and not several cars of train must be 
switched in case of electrical breakdown. 

Granted that an electric locomotive is needed if trunk line 
service is to be electrified, a study of the various types of electric 
locomotives which are in use at the present time is of interest. 
With the many years of experimenting and practical experience 
with steam locomotives which have led to a most satisfactory 
design for the various types of service, advantage was taken of 
present steam locomotive design, and the electrical equipment 
added with as little change as possible. To this end the man- 
ufacturers of steam locomotives and electrical machinery have 
cooperated to a marked degree in developing the new product. 

In the early locomotives it was believed to be necessary, however, 
to mount the motors on the driving axles between drivers as in 
the case of motor cars with consequent limitation in capacity 
of motors if the present gauge of track and short wheel base are to 
be retained. The change of track gauge was of course practically 
impossible with the present installation of standard gauge roads 
in the country and an increase in the length of wheel base in- 
19 



290 



ELECTRIC RAILWAY ENGINEERING. 



troduced difficulties in rounding curves. In fact, any limitation 
upon the flexibility of the truck and the free and independent 
vertical and transverse movement of individual axles with ir- 
regularities in the track tends to move the entire mass of the loco- 
motive, thus introducing bad riding qualities and vibrations which 









1W 




1 








'•- — -*'*T!r^^ 


^HHHE^ 


S^ir 


^ 






,¥^^■1 










d 






8^^- §";,<- ;|;».;^ 




s^^^^^^^^*'^ 


«ir«^'^^i^ 






to 


T 




^: \u..^j 


U 1 fSi 


'!,.•. I ,.,. 






f 


■4 


^^^^^^"'^'^KS 


v.i.^ws_* « 


wk V^^.^ j«C'"'Vl*I_> 


A. . 


/ = « 










IW WW . ^ 


""^ 


wm 


■iMtfS>^S^||^^ 





Fig. 126. 




Fig. 



become dangerous at high speeds. An attempt was first made, 
therefore, to vary the design of the large interurban motors to 
gain greater capacity upon the limited size of trucks and later 
to remove the motor from the truck axles, as will be shown 
below. 

The New York Central locomotive. Fig. 126, of the direct cur- 



ELECTRIC LOCOMOTIVES. 



291 



rent type, a plan view of whose motor is shown in Fig. 127, 
marked a radical departure in railway motor design. As will be 
noted from the figure, the motor is bipolar, the magnetic 
circuit involving a portion of the truck frame with internally 
projecting laminated iron poles with vertical faces, between which 
the armature, mounted directly on the truck axle, might vibrate 
in a vertical direction with the irregularities in the track. This 




Fig. 128. 



design, of course, considerably increased the capacity possible in 
the limited space on the truck, eliminated many of the disad- 
vantages of the small air gap and gave considerable flexibility 
to the relative movement of armature and field. It also lowered 
the center of gravity of the locomotive below that of its steam 
railroad competitor and increased the dead load per axle, both 
of which changes have been considered as disadvantages by 
some engineers. 

The locomotives of the New York, New Haven and Hartford 
Railroad, Fig. 128, which were developed soon after the above 
for operation upon the 11,000 volt single-phase system of the 



292 



ELECTRIC RAILWAY ENGINEERING. 



above company not only, but also upon the 600 volt direct-current 
system of the New York Central Railroad entering New York 
City still retained the motors concentric with the truck axles 
and between the driving wheels as will be seen from Fig. 129, 
but reduced the dead weight upon the axles by supporting the 
armature upon a quill, concentric with, but surrounding the 
driving axle with a space of 5/8 in. between axle and inner cir- 
cumference of quill. The torque was transmitted from armature 




Fig, 



:29. 



to drivers by means of seven driving pins, spring borne in re- 
cesses in the driving wheels as shown in Fig. 130. This allowed 
the axle considerable motion independent of the armature not 
only, but permitted the motor field and frame to be rigidly sup- 
ported upon the truck. 

After some few years of experience with the operation of the 
above locomotives and a careful study of their characteristics as 
compared with steam locomotives, the principle problem in 
design seemed to be resolved to that of the transmission between 
motor axle and driving wheels. Messrs. Storer and Eaton in a 
recent paper before the American Institute of Electrical Engi- 



ELECTRIC LOCOMOTIVES. 



293 



neers^ have presented this problem in a very concise form and 
because of its importance in electric locomotive design and as 
designing engineers in both this country and abroad are at vari- 
ance regarding the best method of transmission to adopt, a state- 
ment of the various types in use, together with illustrations of 
each have been taken from the above paper and are herein 
included. 




Fig. 130. 



a. " Gearless motor with armature pressed onto driving 

axle, 'New York Central,' Fig. 131 a. 

b. " Gearless motor with armature carried on a quill 

surrounding axle, and driving the wheels through 
flexible connections, 'New Haven Passenger,' Fig. 
131b. 

c. " Geared motor with bearings directly on axle and with 

nose supported on spring-borne parts of locomotive, 
'St. Claire Tunnel,' Fig. 132 c. 

d. "Geared motor with bearings on a quill surrounding 

axle, and (i) nose supported on spring-borne parts 
of machine (New Haven Car, Fig. 132 d) and (2) 
motor rigidly bolted to spring-borne parts of machines, 

^ The Design of the Electric Locomotive, by N. W. Storer and G. M. Eaton, 
A. I. E. E., Vol. XXIX. 



294 



ELECTRIC RAILWAY ENGINEERING. 



the quill having sufficient clearance for axle move- 
ments, 'Four motor New Haven Freight, ' Fig. 132 d'. 
e. "Motor mounted rigidly on spring-borne parts, arma- 





ture rotating at same rate as drivers, power trans- 
mitted to drivers through cranks, connecting rods 
and counter shaft on level with driver axles. 'Penn- 
sylvania,' Fig. 133. 



ELECTRIC LOCOMOTIVES. 



295 



f . " Motor mounting and transmission as in (e) but motor 
fitted with double bearings one part for centering 
motor crank axle and the other for centering the 
armature quill which surrounds and is flexibly con- 




FiG. 133. 

nected to the motor crank axle. 'Two motor New 
Haven Freight,' Fig. 134 f. 

'Motors mounted on spring-borne parts, armature 
rotating at same rate as drivers, power transmitted 
to drivers through off-set connecting rods and side 
rods. 'Latest Simplon Locomotives,' Fig. 134 g. 




Fig. 134. 

h. "Motors mounted on spring-borne parts, armature 
rotating at same rate as drivers, power transmitted 
to drivers through Scotch yokes and side rods. 
'Valtellina Locomotives,' Fig. 134 h. 



296 ELECTRIC RAILWAY ENGINEERING. 

i. "Motors mounted rigidly on spring-borne parts, power 
transmitted through gears to counter-shaft, thence 
to drivers through Scotch yokes and side rods. Fig. 
I35-" 

It will be seen from the above that the locomotives of the 
Pennsylvania Railroad mark a rather radical departure from the 
designs previously described, having their motors above the 
trucks in the cab and returning to the connecting rods of the 
steam locomotives for transmission to the drivers. This design 
raises the center of gravity and permits practically unlimited 




Fig. 135. 

motor capacity in a single unit as its dimensions may be increased 
longitudinally at will and transversely by overhanging the driving 
wheels. This locomotive, which is designed in two sections 
which may operate separately, but which are intended for opera- 
tion in pairs, is illustrated in Fig. 136, the slanting driving rod 
seen in the figure connecting with a single motor in each cab 
and being properly balanced by means of a counter-weighted 
crank disc. 

Control Systems. — While the details of the specifications for 
the various types of electric locomotives built thus far in this 
country are concisely set forth in Tables XXVI and XXVII below, 
an additional word regarding the systems of control used may 
be of interest. 

The New York Central locomotives having four 550 H. P., 
600 volt direct current motors each operating upon a third rail 
distribution system have three running steps on their 



ELECTRIC LOCOMOTIVES. 



297 



controllers, the first with all motors in series, the second consist- 
ing of two groups in parallel series and finally all motors in series. 
The control is of the multiple unit type similar to that previously 
described for motor cars with a master controller and train cable 
with coupling plugs so that two or more locomotives may be 
operated together from a single engineer's cab. 




Fig. 136. 



The New York, New Haven and Hartford control equipment 
is the A. C. D. C. unit switch control operating two motors per- 
manently in series. Upon the direct current system of the New 
York Central terminal system the series-parallel control is used 
and upon the high voltage alternating current section the auto- 
transformer steps the voltage down to six different values each of 
which is a permanent running voltage. About double this 
number of steps are required for smooth acceleration upon 
direct current, but because of the motor design used these extra 
steps may be secured in the series position by shunting the fields. 
This may be done in steps until the fields are at about one-half 



298 ELECTRIC RAILWAY ENGINEERING. 

their nominal flux rating without interfering with their successful 
operation. Each locomotive is equipped with four 250 H. P. 
motors nominal capacity, which are capable of exerting 200 H. P. 
each continuously. A pair of motors require 450 volts alternat- 
ing current and 600 volts direct current for full rated speed. 

Each section of the Pennsylvania locomotives contains a single 
motor rated at 2000 H. P. It is of the interpole (10 pole) type 
designed for use upon 600 volts direct current. The motors 
are controlled by the unit switch electro-pneumatic master con- 
trol system previously described, having four running notches as 
follows : 

1. Series connection with full field, 

2. Series connection with normal field, 

3. Parallel connection with full field, 

4. Parallel connection with normal field. 

These locomotives are provided with both third rail shoes and 
trolleys for either type of current collection. 

As has been previously stated the locomotives of the Cascade 
Tunnel Division of the Great Northern Railroad are the only 
examples of polyphase traction in this country. In this par- 
ticular case the installation of a motor with inherent constant 
speed characteristics seemed advisable where long runs over 
practically constant high grades at relatively low speeds were 
demanded. The control of the three-phase motors of these 
locomotives is similar to that for the variable speed slip-ring type, 
phase wound rotor induction motors used in stationary service. 
It consists in inserting resistances in series with the three phases 
of the rotor winding and gradually cutting out these resistances 
in one phase after another by means of a controller. By thus 
varying the resistance of but one phase at a time more accelerat- 
ing points are obtained with less complicated wiring than when 
all three phases are changed simultaneously. This is done, 
however, at the expense of unbalanced currents in the motor and 
would not therefore be advisable under frequent starting condi- 
tions. The motors are of eight poles each, designed for a fre- 
quency of 25 cycles and employ forced ventilation for cooling. 
The voltage is reduced by transformers on the car from 6600 to 



ELECTRIC LOCOMOTIVES. 



299 



500 volts. A speed of approximately 15 m. p. h. is maintained 
in both directions upon an average and fairly constant grade of 
1.7 per cent. 

Data on Electric Locomotives. — The following tables taken 
from a paper by Westinghouse on ''The Electrification of Rail- 
ways" presented before the joint meeting of the American 
Society of Mechanical Engineers and the Institution of Mechan- 
ical Engineers in London in 19 10 represent very concisely the 
details of design of American electric locomotives. 



TABLE XXVI. 



Data on Westinghouse Electric Locomotives. 







Grand 








Built for 


New 


Trunk 


Pennsyl- 


New 


New 


Haven 


St. Clair 


vania 


Haven 


Haven 






Tunnel 








Electric system 


A. C.D.C. 


A. C 


D. C 


A. C. D. C. 


A. C. D. C. 


Service ^ 


Passenger 


Frt. & Pass. 


Passenger. 


Frt. & Pass. 


Frt. & Pass 


First placed in service 


July 1907 


Feb. 1908.. 


17,000- 
mile test. 


3,000-mile 
test. 


Building. 


No. in service or on order, 


41 


6 


24 


I 


I 


May, 1910. 












No. motors per locomotive. 


4 


3 


2 


4 


2 


Armature diameter, inches . 


39* 


30 


S6 


39i 


76 


Core length, including vent. 


18 


14I 


23 


13 


13 


opening, inches. 












Weight I motor, pounds. . . . 


16,420 


15,660 


45,000 


19,770 


41,600 


Wt. all motors on locomotive 


65,680 


46,980 


90,000 


79,080 


83,200 


Wt. all electrical parts 


110,400 


58,400 


127,200 


130,000 


135,000 


Wt. all mechanical parts . . . 


94,100 


73,600 


204,800 


130,000 


125,000 


Wt. complete locomotive. . . 


204,500 


132,000 


332,000 


260,000 


260,000 


Wt. on driving wheels 


162,000 


132,000 


207,800 


180,000 


180,000 


Wt. complete locomotive 


196,000 


132,000 


D. C 


241,000 


240,000 


for A. C. operation. 












Max. guar't'd speed m.p.h. 


About 86 


30 


About 80 


45 


45 


Feature limiting speed 


Track. . . . 


Armature... 


Connecting 
rod. 


Armature. . 


Armature. 


Max. tractive effort 


19,200 


43,800 


69,300 


40,000 


40,000 


Loco. wt. in excess of i8% 


88,700 


None 


None 


18,500 


17,500 


adhesion Max. T. E., A. C. 












operation. 












Designed for trailing load, 


250 


500 


550 


/ 1500 frt. 


/ 1500 frt. 


tons. 








\ 800 pass. 


1 800 pass. 


Balance speed on level with 


About 75 


About 2 5 


60 


3 5 frt. 


3 5 frt. 


above load. 








45 pass. 


45 pass. 



300 



ELECTRIC RAILWAY ENGINEERING. 



TABLE XXVII. 

Data on General Electric Locomotives. 



Built for 



N. Y. C. Detroit 
& River 

H. R. R. Tunnel 



B. &0. R.Rl 



Great 

Northern 



Paris- 
Orleans 



Electric system 

Service 

First placed in service. 



No. in service or on order 

May, 1910. 
No. motors per locomotive. 
Armature diameter, inches. 
Core length, including vent. 

opening, inches. 

Wt. one motor, pounds 

Wt. all motors on locomotive 

Wt. all electrical parts 

Wt. all mechanical parts . . . 
Wt. complete locomotive. . . 

Wt. on driving wheels 

Wt. complete locomotive 

for A. C. operation. 
Max. guar't'd speed, m.p.h. 

Feature limiting speed 

Max. tractive effort 

Loco. wt. in excess of 18% 

adhesion Max. T. E., A. C. 

operation. 
Designed for trailing load, 

tons, Freight 

Passenger 

Balance speed on level with 

above load. 



D. C... 
Passenger 
July 1906 

47 

4 
29 

19 

18,150 

72,600 

91,200 

138,800 

230,000 

141,000 

D.C 



75 
Track . . . 
47,000 
None. . . . 



45 
63 



D. C 

Frt. & Pass 
Tests com- 
pleted. 
6 

4 
25 
ii4 

10,560 

42,240 

54,000 

146,000 

200,000 

200,000 

D. C 



30 
Armature. 

67,000 
None 



900 on 2% 
600 grade. 
Frt. 20.5 
Pass. 22 



D. C 

Frt. & Pass. 
March 1910 



4 

25 



10,560 

42,240 

54,000 

130,000 

184,000 

184,000 

D. C 



55 
Armature. 
61,000 
None 



850 on ii% 
500 grade. 
Frt. 26 
Pass. 30 



3 -phase. . 
Frt. & Pass. 
July 1909 . 



4 
3Sl 
i6i 

15,000 
60,000 
109,000 
121,000 
230,000 
230,000 
230,000 

30 
Armature. . 

77,000 
None 



500 on 
2.2% grade 
IS 



D. C. 

Passenger. 
1899 



4 

23* 

12 

8,855 

35>420 

42,500 

67,500 

110,000 

110,000 



D. C. 



45 
Armature. 

37,000 
None. 



300 
32 



Although some arguments in favor of the electric locomotive 
as compared with its steam rival will be considered in a later 
chapter, it may be said in the conclusion of this discussion that 
the electric locomotive has accomplished thus far all that has 
been required of it, i.e., to -operate as satisfactorily as the steam 
locomotive under all conditions of service and eliminate the 
disadvantages coincident with smoke and dirt of the latter. It 
has also shown itself capable of accelerating more rapidly than 
its competitor, which particularly commends it where headway 
is short and stops are frequent. It can readily be designed for 
a draw bar pull considerably in excess of that of the largest steam 
locomotives. It has therefore found a permanent place in the 



ELECTRIC LOCOMOTIVES. 



301 



electrification of terminals and its future now seems to be one of 
further adaptation and adoption, although its depreciation and 
maintenance in comparison with the steam locomotive can hardly 
be intelligently compared at present. 

Gasolene Electric Car. — Although not strictly confined to the 
function of a locomotive, the gasolene electric car should be given 




Toilet' 
2 5i^"s 3'3%" 

Fig. 137. 



a place in the discussion of electric traction. In several instances, 
particularly upon small branch roads acting as feeders to trunk 
lines, where traffic is light and the installation of an electrical 
distribution system therefore unwarranted, and yet where the 
advantages of electric traction are worthy of serious considera- 
tion, the gasolene electric car has found a place. This car not 
only provides for from 40 to 50 passengers, together with a 




baggage compartment, but also is a complete power plant, a 
flexible distribution system and a motor car combined. In the 
front end, above the floor, is located an eight cylinder, 100/125 
H. P. four-cycle-gasolene engine, direct connected to an 80 K. W., 
600 volt commutating pole direct current generator with exciter. 
A series parallel controller regulates the supply of current from 



302 ELECTRIC RAILWAY ENGINEERING. 

this generator to two loo H. P. motors mounted on the front 
trucks. Additional flexibility of control is provided by the 
regulation of the voltage supplied to the motors by the variation 
of the generator field strength. The controller is also provided 
with means for regulating the engine ignition and the throttle. 
The car may be started, stopped, and reversed with the engine 
running continuously in one direction. A trolley is often pro- 
vided by means of which the car may be operated on standard 
direct current trolley systems without change in the control 
equipment. 

Reports from roads where these cars have been installed show 
a marked reduction in operating expenses and maintenance 
charges over those of steam operated trains, although their com- 
paratively recent introduction has not permitted an accurate 
comparison over an extended period. A plan and elevation of 
one of these cars may be found in Figs. 137 and 138 respectively. 



PART IV. 

TYPES OF SYSTEMS. 



CHAPTER I. 
Alternating Current vs. Direct Current Traction. 

The problem to be discussed under the above caption is one 
that has received much attention during the past few years by 
steam and electric railroad officials, consulting engineers and 
electrical manufacturing companies. It has been the target of 
much discussion before technical societies and in the technical 
press, at times involving rather heated criticisms based upon 
both accurate engineering data and the enthusiastic prophecies 
of more or less prejudiced engineers. To sift out the salient 
factors in the case and outline the present status of the problem 
in a few words becomes, therefore, a difficult task. 

Whereas the greater part of the discussion of this subject has 
been in connection with the electrification of steam roads, because 
of the prominence of the latter problem at the present time, before 
which the selection of a motive power for an interurban system 
immediately becomes dwarfed in magnitude, yet the consideration 
of this latter subject has purposely been made to precede that of 
"Electric Traction on Trunk Lines" because of its broader 
applicability to interurban systems, steam railroad electrification 
and possibly to city traction systems under some peculiar local 
conditions. 

The systems which have sufficient advantages and for which 
complete power station, distribution and rolling stock equipment 
have been sufficiently developed to warrant consideration in this 
problem are the following. 

1. Polyphase system, 

2. Direct current 600 volt system, 

3. Direct current 1200 volt system, 

4. Single phase high voltage system. 

The polyphase system, although least important, has been 
considered first for the reason that it may be readily classed 
separately and therefore omitted from the more detailed com- 

20 305 



306 ELECTRIC RAILWAY ENGINEERING. 

parison which follows. The following characteristics of the 
polyphase system prevent its selection except for very special 
cases in which speeds may be low and constant, stops infrequent, 
service and grades heavy and fairly constant and operation with 
relatively low efficiency and complicated control not objection- 
able. 

a. Constant speed characteristics, 

b. Only the one-half and full speed operation efficient, 

c. Control equipment complicated, 

d. Unbalanced motor currents during acceleration, 

e. Complicated distribution system involving either three 
trolley wires and three trolleys per car or two of each of the above 
with a track return for the third phase, 

f. Cannot be operated upon direct current. 

With the above explanation of the peculiar conditions under 
which the polyphase system must operate, which has thus far 
limited its installation to a single road in this country which has 
been previously described herein, the remaining three systems 
will be compared upon as nearly the same basis as possible. The 
peculiarities of each system, which may result in advantages or 
disadvantages depending upon local conditions in each instal- 
lation, will be discussed in connection with the several determining 
and distinctive functions of the complete railway system. 

Power Station. — The power station is not materially different 
for the three systems for a long road, involving as it does three- 
phase generating equipment and step-up transformers, together 
with the control of three-phase high tension transmission lines. 
If the single phase system be operated with a single-phase gener- 
ating station, which is the exception rather than the rule, the 
first cost and size of generating equipment are increased for a 
given output, but the switchboard and control are slightly 
simplified. 

Transmission Lines. — No material difference exists between 
the systems in regard to transmission, so long as three-phase 
transmission is adopted. The costs of these lines for all three 
systems are therefore practically identical. In the compara- 
tively few installations where single-phase transmission might 
be adopted, the design and construction of the line is simplified 



ALTERNATING VS. DIRECT CURRENT TRACTION 307 

by the use of two wires in place of three, but for a given power 
transmitted and a fixed efficiency of transmission the cost of 
copper in the three-phase system is 25 per cent. less. This 
will usually more than balance the added installation and main- 
tenance cost of the third wire. 

Substation. — In the design of the substation is found one of 
the most marked variations in the three systems. As explained 
in a previous chapter the two direct current systems require the 
installation of transformers, synchronous converters or motor 
generators and switchboards in the substation, whereas the alter- 
nating current system calls for the transformers and automatic 
control switches only. This not only greatly reduces the first cost 
and maintenance in the latter system, but eliminates the services 
of an attendant. The elimination of this converting equipment 
will be found from the tables listed below to lower the first cost of 
substation to 27 per cent, and 37.5 per cent, of the 600 volt and 
1200 volt substations respectively, while the operating costs are 
reduced respectively to 26.2 per cent, and 58.2 per cent, of the 
direct current substations. This is not clear gain on the part of 
the single-phase system, however, as it is partially balanced by 
the increased cost of rolling stock in the latter system. 

In the relatively few instances in which the increase in dis- 
tribution voltage in the single-phase system is sufficient to permit 
the economical transmission for the entire length of the line at 
trolley potential, the substation cost and maintenance is not 
only entirely eliminated, but the step-up transformers at the 
power station may usually be eliminated as well and the switch- 
board considerably simplified in consequence. 

If the single-phase equipment were as well developed and 
standardized as the 600 volt direct current apparatus a lower 
depreciation factor might be applied to the former substation 
because of the relatively shorter life of the commutating machinery 
of the latter station, but it is probable that the allowance for 
obsolescence which must be made in the depreciation charges on 
recently developed equipment will compensate for any such re- 
duction. 

The first cost of the 1200 volt direct current substation is but 
73 per cent, of the 600 volt station because of the lower current 



3o8 ELECTRIC RAILWAY ENGINEERING. 

value necessary for the same output, thereby reducing the size 
and cost of converters, cables and switchboard. 

Distribution System. — As would naturally be expected the 
first cost of the distribution system decreases with increase of 
voltage, thereby favoring the 1200 volt direct current and 3300 to 
11,000 volt single phase systems, especially in cases where traffic 
is sufficiently heavy to require the installation of the third rail 
in case of the 600 volt system. While this gain in first cost is 
admitted by the advocates of the direct current system in case of 
wooden pole line construction attention is called to the fact 
that with so-called "permanent" overhead construction, referring 
to the double catenary supported on steel bridges with long spans, 
the cost of the overhead is quite equal to that of the third rail 
construction. 

Rolling Stock. — With the equipment of rolling stock 
the pendulum of efficiency, first cost and possibly of main- 
tenance swings in the other direction favoring the direct current 
system. 

Single-phase motors in their present stage of development 
are generally believed to be slightly inferior to the direct current 
motor in efficiency and quick accelerating qualities for a given 
rating. They are also considerably heavier for a given output, 
thus increasing the weight of car to be accelerated for a given 
traffic return. The above are general conclusions which will 
probably be conceded by both factions that have entered the 
rather extended controversy regarding the relative advantages 
and disadvantages of the single-phase motor for traction pur- 
poses. That this question is far from being decided is illustrated, 
however, in the following discussions of the subject before the 
American Institute of Electrical Engineers, which have been 
quoted herein for the double purpose of pointing out the 
unsettled condition of single-phase motor development at the 
present time as well as illustrating the various details of design 
under question. 

Sprague points out the following differences between the single- 
phase and direct current motors. ^ 

^ ''Some Facts and Problems Bearing on Trunk Line Operation," by Frank J. 
Sprague, A. I. E. E., Vol. XXVI. 



ALTERNATING VS. DIRECT CURRENT TRACTION. 309 

''i. The input of current in one is continuous; in the other 
intermittent. 

"2. One has a single frame, the electrical and mechanical parts 
being integral; the other has a laminated frame contained within 
an independent casing. Hence there is not equal rigidity, or 
equal use of metal. 

"3. One has exposed and hence freely ventilated field-coils; 
the other has field-coils imbedded in the field-magnets. 

"4. One has a large polar clearance, and consequently ample 
bearing- wear; the other has an armature clearance of about only 
one-third as much, and hence limited bearing-wear, 

''5. One is operated with a high magnetic flux, and conse- 
quently high torque for given armature-conductor current; the 
other has a weak field, and consequent lower armature torque. 

"6. One has a moderate sized armature and commutator, and 
runs at a moderate speed; the other, with equal capacity, has a 
much larger diameter of armature and commutator, and runs 
at a much higher speed. 

"'J. One permits of a low gear-reduction, and consequently a 
large gear-pitch; the other requires a higher gear-reduction, and 
a weaker gear-pitch. 

"8, The windings of one are subject to electrical strains of one 
character; in those of the other the strains are of rapidly variable 
and alternating character. 

"g. The mean torque of one is the corresponding maximum; 
the mean torque of the other is only about two-thirds of the 
maximum. 

'^ 10. The torque of one is of continuous character; that of the 
other is variable and pulsating, and changes from nothing to the 
maximum fifty times a second. 

''11. One has two or four main poles only, two paths only 
in the armature, and two fixed sets of brushes; the other has 
four to fourteen poles, as many paths in the armature, lead- 
ing to unbalancing, and as many movable sets of commutator 
brushes. 

''12. One can maintain a high torque for a considerable time 
while standing still; the other is apt to burn out the coils, which 
are short circuited under the brushes. 



3IO ELECTRIC RAILWAY ENGINEERING. 

"13. In one, all armature-coil connections are made directly 
to the commutator; in the other, on the larger sizes resistances 
are introduced between the coils and every bar of the commutator, 
some of which are always in circuit, and the remainder always 
present. 

'^ 14. In one the sustained capacity for a given weight is within 
the reasonable requirements of construction; in the other it is 
only about half as much. 

"15. Finally, the gearless type, with armature and field vary- 
ing relatively to each other, is available for one, but this con- 
struction is denied to the other. 

''Consideration, then, of the characteristics peculiai to each 
class of motor indicates not that the single-phase motor cannot 
be used, but that if adopted the weight or number, and the cost 
of locomotives or motors required to do the work must be much 
greater; that the depreciation of that which is in motion will be 
much higher; and that there will always be an excess weight of 
fixed amount per unit which must be carried irrespective of the 
trailing or effective loads. We must, therefore, in many cases 
be led to the selection of the direct-current motor, that motor 
which has the higher weight capacity, the greater endurance, and 
the lower cost per unit of power." 

In discussing this paper Storer criticizes each point in turn 
as quoted below. ^ 

"i. 'The input of current in one is continuous; in the other, 
intermittent.' Quite true, but the draw-bar pull is quite as 
effective in one case as in the other. 

" 2. The direct-current motor has a solid frame like the single- 
phase motor. It has, further, two or more laminated poles 
bolted in, and if the interpole construction is used has as many 
more relatively small and delicate poles. The alternating- cur- 
rent motor as built by the company with which I am connected 
has, in all sizes up to a diameter of ^S in. field punchings made 
in a single piece and built up and keyed in the frame/ making 
it as solid a construction as an armature on its spider. The 
claim for less rigidity in the single-phase motor is, .therefore, not 
sustained. 

^Discussion of above paper by N. W. Storer, A. I. E. E. Vol. XXVI. 



ALTERNATING VS. DIRECT CURRENT TRACTION. 31I 

''3. 'One has exposed and hence freely ventilated field-coils; 
the other has field-coils embedded in the field-magnets.' It is 
known to most motor designers that coils in contact with iron 
will dissipate heat much faster than when in the open air. This is 
especially true of coils in an enclosed motor. I have repeatedly 
noticed that motor field-coils which have been removed on 
account of roasting, have shown the insulation in contact with 
the pole pieces to be in good condition, while other sides were 
badly roasted. I know, therefore, that in respect to ventilation 
of field-coils, the single-phase motor is superior to the direct- 
current motor. Smaller cross-section of coils also allows the 
heat to be radiated better in single-phase motors, and the fact 
that a large part of the loss in the motor is concentrated in the 
field iron will enable the motor to dissipate a much larger amount 
of heat for a given temperature-rise than will a direct-current 
motor. 

"4. Concerning 'polar clearances.' Many thousands of 
direct-current motors are to-day in operation with a clearance of 
1/8 in. to 3/16 in. between poles and armatures, and in practi- 
cally all cases where more than 3/16 in. clearance is used it is for 
electrical reasons. Further, while the smaller air-gap used for 
single-phase motors was at first much feared, the fears have 
proved to be without foundation and the present clearances of 
from 0.1 in. to 0.15 in. have proved to be ample and fully as 
good as 0.15 in. to 0.25 in. in direct-current motors, because 
there is no unbalanced magnetic pull. 

''5. Concerning 'torque.' The torque of an armature is the 
pull it will exert at one-foot radius. Therefore it makes no dif- 
ference in the result whether it is obtained with large flux and 
few armature conductors, or vice versa. 

"6. 'A much larger diameter of armature and commutator, 
and runs at a much higher speed.' This is a very general state- 
ment: what are the facts? The armature diameters ordinarily 
run from 5 to 15 per cent, larger than for direct-current motors of 
corresponding output. It is undoubtedly true that the armature 
speeds of the earlier single-phase motors were much higher 
than the speeds of corresponding direct-current motors; at the 
present time, however, the speed at the nominal rating of the 



312 ELECTRIC RAILWAY ENGINEERING. 

motor is practically the same as that of direct-current motors, 
and the maximum operating armature speeds are within the 
safe limits set for direct-current motors. 

"7. Concerning 'gear-reduction and gear-pitch.' The gear- 
reduction depends, of course, upon the speed; and as far as gear- 
pitch is concerned, I wish to say that the same gear-pitch is used 
for single-phase motors as for direct-current motors of the same 
capacity. 

"8. 'The windings of one are subject to electrical strains of 
one character; in those of the other the strains are of rapidly 
variable and alternating character.' No conclusion is drawn 
from this. It may be of interest to know that there have been a 
number of instances where the single-phase motor has broken 
down in service on a direct-current section of the line, necessi- 
tating cutting it out of the circuit; but when the car reached the 
alternating- current section of the line it has been again connected 
in circuit and operated satisfactorily, thus indicating that the 
"electrical strains with alternating current are less severe than 
with direct current. 

"g and 10. Concerning the 'variable torque of the single-phase 
motor.' No comment is made as to the relative merits of uniform 
or pulsating torque. In a recent discussion before the Institute, 
Mr. Potter called attention to certain characteristics of the torque 
exerted by an alternating-current motor, especially when it 
reaches the slipping point of the wheels. It was stated that there 
is an apparent advantage in the pulsating torque, because, when 
the motor starts to slip it does not immediately decrease its mean 
torque, as is done in the case of the direct-current motor, but 
slips in a series of jerks, apparently regaining the hold on the 
rail at every pulsation. 

"11. Concerning the 'number of poles.' The paper states 
that the direct-current motor has 'two or four main poles only.' 
No direct- current motors built in the last 15 years except those on 
the New York Central locomotives have less than four poles. 
The paper states that the alternating-current motor has 
'eight to fourteen poles.' The single-phase motors built by 
the company with which I am connected have four poles for 
all si^es up to and including 125 h. p. The largest single- 



ALTERNATING VS. DIRECT CURRENT TRACTION. 



3^3 



phase motor thus far built has a capacity of 500 h. p. It has 
but 12 poles. 

"12. Concerning 'a high torque while standing still.' As we 
understand the matter, railway motors are designed to move a 
train rather than to hold it at rest. At the same time we know 
that the single-phase motor is amply protected against mistakes 
of motormen in leaving the current on the motor for a half- 
minute or so with brakes set. 

''13. Concerning 'resistance in commutator leads.' It is well 
known that the resistance leads used in single-phase armatures 
are for the purpose of reducing to a minimum the loss due to the 
transformer action in the short-circuited coil. Their presence is 
fully justified and the efficiency is higher than it would be if 
they were not used. 

"14. This refers to relative weights concerning which I shall 
have something to say farther on. 

"15. On this point I agree absolutely with the author. 
There is one type of construction to which the single-phase 
motor is not adapted. This is so far employed in only a single 
case. 

"More or less is said in the paper concerning the lower effici- 
ency of the single-phase motor, and inference might be drawn 
that it is about 10 per cent, lower than that of the corresponding 
direct-current motor. Just to show what modern motors are 
capable of doing, I give below in parallel columns the efficiencies 
of corresponding sizes of direct- and alternating-current motors 
at different percentages of their full-load torque. 



Per cent, of 
full-load 
torque 



Direct current 
90 h. p. motor 



Alternating cur- 
rent 25-cycle, 
100 h. p. motor 



Direct current 
200 h. p, motor 



Alternating cur- 
rent IS -cycle, 
200 h. p. motor 



I2S 
100 
80 
60 
40 
25 



86.25 


82.0' 


88.8 


87. 


86.8 


85.0 


89-0 


88. 


87.0 


86.0 


89.2 


88. 


86.5 


86.8 


88.8 


87. 


85.0 


86.0 


87.0 


85. 


82.0 


82. 5 


84.0 


82. 



314 ELECTRIC RAILWAY ENGINEERING. 

The added weight, lower efficiency, and lower acceleration 
for a given capacity of motor are not the only disadvantages of 
the alternating current system from the standpoint of rolling 
stock. As has been pointed out, it is nearly always desirable 
that cars equipped for alternating current service be able to enter 
cities upon direct current. While the alternating current single- 
phase series motor makes an excellent direct current motor, the 
control equipment for use upon either system is at best rather 
coinplicated and its first cost, weight and maintenance relatively 
high. ] The added complication of this combined control is at 
once obvious if a comparison be made of Figs. 104 and no, while 
the tables listed below prove the rolling stock thus equipped to 
cost 28 per cent more, with a probable maintenance charge of 
49 per cent, more than the 600 volt direct current equipment. 

Referring to the 1200 volt direct current system, the motors' 
are often of the 600 volt type which has been well standardized. 
Upon the city systems they operate as standard 600 volt equip- 
ment connected in parallel for full speed, while upon the 1200 
volt trolley they are connected two in series for full speed opera- 
tion. In cases where only half speed operation is required 
within the city limits, 1200 volt motors similar to the 600 volt type 
are used, the current capacity, of course, being less for a given 
car and extra insulation being provided for the higher voltage. 
Although the high voltage direct current equipment has not been 
standardized and thoroughly tried out in practice as yet, the 
dozen or more roads in operation are apparently giving satis- 
factory results, while the first cost and maintenance cost are but 
slightly greater than the low voltage system. 

First Cost and Maintenance. — The relative merits of the 
three systems from the standpoint of first cost and maintenance 
expenses can best be illustrated by means of tables XXVIII 
and XXIX taken from a very able discussion of the subject 
before. the American Institute of Electrical Engineers by W. J. 
Davis, Jr.^ 

^ ''High Voltage Direct Current and Alternating Current Systems for Interurban 
Railways," by W. J. Davis, Jr., A. I. E. E., Vol. XXVI. 



ALTERNATING VS. DIRECT CURRENT TRACTION. 



315 



TABLE XXVIII. 

Comparative Cost per Mile Single Track. 



D. C. 600 V. D. C. 1200 V. A. C. 6600 V. 



Road bed, complete including grad 
ing, ballasting, etc. 

Trolley and feeder installed 

Track bonding 

Transmission line installed 

Substation installed 

Power station installed 

Cars and equipment 

Telephone 

Saving over 600 volts D. C 



515,000 

3,800 
600 

1,500 
2,200 

2,450 

1,800 

120 



27,470 



;i5,ooo 

3,000 

530 

1,500 

1,600 

2,450 
1,970 

120 



26,170 

1,300 



,15,000 

2,100 

480 
1,300 

600 

2,570 
2,300 

120 



24,470 
3,000 



TABLE XXIX. 

Relative Operating Cost per Mile Single Track per Annum. 
(One hour headway). 




Car miles per day 

Kw. hours per day at power house . . 



Cost of coal per annum 

Cost of substation attendance 

Maintenance of motors and control. 

Total 

Saving over 600 V. direct current ex- 
clusive of fixed charges. 
Saving in fixed charges 



$470 

17s 
94 



$470 

79 
117 



^419 

46 

140 



$739 



666 
76 

137 



605 
134 

315 



Total annual saving. 



$213 



449 



The above comparative costs are based upon the following 
data: 

Length of road, 50 miles or more. 

Cars, 52 ft. over all, weighing 21 tons, without equipment or 
load and seating 56 passengers. 



3i6 



ELECTRIC RAILWAY ENGINEERING. 



Car equipment, four 75 h. p. motors. 
Maximum speed on tangent level track, 45 m. p. h. 
Schedule speed, 24 m. p. h. including stops and slow running 
through towns. 

Headway, maximum service, one-half hour. 

Frequency of stops, one in two miles. 

Average energy, 85 watt-hours per ton mile at car. 



D. c. 600 V. 



D. C. 1200 V. 



A. C. 6600 V. 



Spacing of substations 

Maximum trolley voltage drop 

Efficiency, generator bus bars to cars 
Average efficiency car equipment. . . . 
Average power factor of system . . . . , 



10 mi. 

25% 
71% 
75% 
96% 



22 mi. 

25% 
71% 
75% 
96% 



32 mi. 

10% 

84% 

73% 
85% 



Power Factor. — The last factor included in the above list 
emphasizes one other disadvantage of the single-phase system, 
i.e., its low uncontrollable power factor. The direct current 
system has no apparatus on the car or between the car and the 
converters to lower the power factor and its converters may 
even permit the power factor of the transmission line to be 
raised. The single-phase system, with no converting apparatus 
offers no means of power factor control, while the power factor is 
lowered still further beyond the substation by car motors, trans- 
former, steel messenger or trolley if used and rails. A lower power 
factor means higher proportional current for a given capacity 
with increased first cost of equipment and percentage losses. 

Frequency. — Another much discussed factor is that of fre- 
quency, if the single-phase system is being considered. Although 
a frequency of 25 cycles has been standardized for power supply 
and lower frequency apparatus is at present special and there- 
fore high in first cost and slow of delivery, the introduction and 
future standardization of a 15 cycle frequency for railway service 
has been seriously advocated by many railway engineers for the 
following reasons. 

I. An increase of from 30 to 40 per cent, in output of a motor 
of given size. 



ALTERNATING VS. DIRECT CURRENT TRACTION. 317 

2. Consequent reduction in motor capacity required. 

3. Consequent reduction in first cost of motor equipment. 

4. Higher motor efficiency. 

5. Higher motor power factor. 

6. Better commutation. 

7. Less dead weight on axles. 

8. Lower line losses. 

In contrast to these advantages of low frequency may be listed 
the impossibility of supplying lighting loads from the same 
generators with this frequency, the already established standard 
of 25 cycles, unsatisfactory turbine design in small sizes and the 
higher cost and greater weight of transformers. 

At present there is no 15 cycle railway system in this country 
and it rests with the engineers of the future to decide whether the 
above advantages of low frequency are to dominate the selection 
of equipment for the individual roads if alternating current 
traction be determined upon. The opinion has been often 
expressed by^ prominent engineers that if the single-phase rail- 
way motor can be improved, the elimination of the converting 
apparatus in the substation and the lower first cost of the entire 
system will soon bring about a more general adoption of single- 
phase traction. Whether the lowering of the frequency to 15 
cycles is the means to this end or not is yet to be decided. 

In conclusion, it may be said that the tendency in electric trac- 
tion as in every other branch of electrical development is toward 
higher voltages. The advocates of direct current traction point 
out the advantages of the 1200 volt system over the once almost 
universal system operating at 600 volts. In a recent paper before 
the American Institute of Electrical Engineers a conservative 
estimate of the economy obtained by a 1200 volt direct current 
system as compared with the 600 volt system as far as the factors 
are concerned which are dependent upon choice of system was 
given as follows.^ 

First cost, 10 to 20 per cent. 

Fixed charges, 10 to 18 per cent. 

Operation and maintenance, 10 to 15 per cent. 

^ "The 1200 volt railroad: A Study of Its Value for Interurban Railways," by 
Charles E. Eveleth, A. I. E. E., Vol. XXIX. 



3l8 ELECTRIC RAILWAY ENGINEERING. 

If the argument be carried but a step farther, the favored 
system of the near future would naturally be that one capable 
of transmitting power to the car at still higher voltages, which 
seems to point at present to alternating current propulsion of cars. 
This tendency in the near future should be greatly strengthened 
by the possible elimination (with the alternating current system) 
of the converter substation and its attendant operating troubles 
and expense and the lower first cost of the latter system where 
taken as a whole. All history of science and engineering is 
opposed to the feeling that the present condition of the alternating 
current system is as efficient and simple as it can be made and 
it therefore seems quite probable that the few unsatisfactory 
features of the alternating current motor and control design will 
soon be overcome and the single-phase system enjoy a much 
extended application to long distance traction. It will remain 
for the consulting engineer, however, to decide in each individual 
case upon the merits of the three or more systems, and the above 
statements should not be interpreted, therefore, as a prediction 
that alternating current traction will be eventually installed in 
all interurban developments nor that it necessarily is, or ever 
will be, the solution of trunk line electrification. 



CHAPTER II. 
Electric Traction on Trunk Lines. 

The late E. H. Harriman is quoted in the New York Times 
as having said : 

"But perhaps it is chimerical to think now of rebuilding the 
railroads of the entire country, and of replacing the entire rail- 
road equipment. If so, what is the best thing? Obviously, 
electricity. And I believe that the railroads will have to come 
to that, not only to get a larger unit of motor power and of dis- 
tributing it over the train load, but on account of fuel. That 
brings up another phase of the existing conditions. We have 
to use up fuel to carry our fuel, and there are certain limitations 
here just as much as there are in car capacity or motive power, 
particularly when you consider the distribution of the coal pro- 
ducing regions with respect to the major avenues of trafhc. The 
great saving resulting from the use of electricity is apparent, 
quite aside from the matter of increasing the tractive power and 
the train load. 

"The only relief which can be obtained through economics 
of physical operation must come through the outlay of enormous 
amounts of money such as would be involved in a general electri- 
fication or change of gauge." 

This statement coming from such an eminent steam railroad 
authority, together with the already completed electrification of 
the terminals of the three large steam railroads entering New 
York, the Hoosac Tunnel of the New York, New Haven and 
Hartford Railroad, the Cascade Tunnel of the Great Northern 
and many other sections of former steam railroads throughout 
the country must convince the most prejudiced opponent of elec- 
trification that the time has come for the serious study of the prob- 
lem of trunk line electrification. Thus far the electrification of 
steam roads has been adopted to meet special requirements or to 
solve pecuhar problems in traction, such as the necessity of in- 

319 



320 ELECTRIC RAILWAY ENGINEERING. 

creased service in large terminals, the avoidance of smoke in 
tunnels and the decrease of headway upon single track mountain 
grades. It may be safely predicted, however, that these special 
problems will gradually increase, the electrified terminal divisions 
gradually encroach upon the trunk line and eventually all will be 
electrically operated. 

Probably the two paramount questions in the minds of steam 
railroad directors in connection with this problem are : 

1. Can the service be improved with electric traction? 

2. What will it cost to change and to operate and maintain 

the new system when installed ? 
While it seems advisable to consider these questions, especially 
the second, more in detail subsequently, a few of the minor ad- 
vantages of electric traction on trunk lines, most of which are 
involved in the first question of possible improved service, will be 
first considered. The outline of the following brief discussion 
is one presented in great detail in the very valuable paper by 
Messrs. Stillwell and Putnam before the American Institute of 
Electrical Engineers.^ 

The factors entering into passenger service which contribute 
to the earning power of the electrified road to a greater extent 
than the steam railroad are : 

Frequency of service. 

Speed. 

Comfort of passengers. 

Safety. 

Reliability of service. 

Increased capacity of line. 

Frequency of stops. 

Convenient establishment of feeder lines. 

Frequency of Service. — Experience with high speed inter- 
urban lines paralleling steam lines, but offering much more fre- 
quent service as illustrated in Table III, Part I, leads to the con- 
clusion that frequent service creates traffic and therefore increases 
earning power. The frequent service offered by an electrified 
system is usually impractical with steam operation. 

^ "On the Substitution of the Electric Motor for the Steam Locomotive," by 
Lewis B. Stillwell and Henry St. Clair Putman, A. I. E. E., Vol. XXVL 



ELECTRIC TRACTION ON TRUNK LINES. 32 1 

Speed. — Higher average speeds are possible and practical in 
electric service for four principal reasons. 

a. The absence of reciprocating parts reduces danger of the 
locomotive leaving the track. 

b. The absence of reciprocating parts reduces the maintenance 
of the track and the liability of broken rails. 

c. The more rapid acceleration permits higher average speed 
with the same number of stops, or more stops with the same 
schedule speed. 

d. For heavy trains requiring two locomotives, high speeds 
can be maintained by means of the multiple-unit control system. 
This is unsafe with two steam locomotives, as both engines cannot 
be controlled by a single engineer. 

Comfort of Passengers. — The general comfort of passengers 
is greatly enhanced by the following features of electric traction : 

a. Elimination of smoke and cinders. 

b. Improved ventilation of cars made possible because of the 
absence of smoke and cinders. 

c. More efficient and satisfactory car lighting possible, although 
unfortunately not always provided. 

d. Easily conti'olled car heating. 

Safety. — Several very notable elements of danger which are 
present in steam traction are eliminated when electrification is 
complete. 

a. The power may be shut off by the train dispatcher to avoid 
collision. 

b. The results of the absence of reciprocating parts which 
permit higher speeds to be maintained as outlined under the 
caption "Speed" also reduce the probability of accident. 

c. If a collision occurs, the power may be promptly cut off if 
it is not accomplished automatically, as is usually the case. 

d. The absence of the intense fire of the locomotive reduces 
the probability of fire in the wreckage. 

e. The elimination of hot water and steam in locomotive and 
heating system reduces the dangers often resulting from such 
sources. 

f. The absence of smoke in tunnels prevents errors in reading 
signals from that cause. 

21 



322 ELECTRIC RAILWAY ENGINEERING. 

g. Less likelihood of fire from electric lighting than from the 
oil or gas lamps commonly used upon steam roads. 

h. The presence of a source of electrical power along the 
roadway and the necessary employment of electrically trained 
maintenance crews should decrease the first cost and maintenance, 
and therefore increase the use of automatic block signals. 

It must be remembered, however, that in contrast to these 
advantages, the electrical distribution system, especially the 
third rail, offers a danger not present in steam railroad operation. 
Whereas the third rail may be protected, thereby reducing the 
danger under normal operation to a minimum, such protection 
would avail little in the case of a wreck. Under these circum- 
stances the automatic circuit breakers must be relied upon to 
disconnect the section from the source of supply before 
serious physiological effects are produced or fires started in the 
wreckage. 

Reliability of Service. — Comparison of the train delays from 
all causes, both electrical and mechanical, before and after elec- 
trification upon the few roads which have been operating suffi- 
ciently long by electricity to guarantee dependable results points 
to the conclusion that the service is more reliable after electri- 
fication than before. 

For example, upon the Manhattan division of the Interborough 
Rapid Transit system of New York after electrification, the 
delay during the most severe months of the year for the 
exposed third rail system was but 72 per cent, of that under 
steam operation, expressed in train minutes, although an 
increased car mileage of 37 per cent, was maintained with the 
electric service. 

Upon the electrified section of the New York, New Haven 
and Hartford Railroad during the heaviest traffic day of the year 
occasioned by the annual foot-ball game at New Haven, 128 
regular trains and 30 special trains were operated between New 
York and New Haven in 1908 with but two delays totaling 17 
minutes, while in 1909, 155 trains were run with no delays 
whatever. 

The electrified system of the Grand Trunk Railway in the 
St. Clair Tunnel has operated six single-phase locomotives, each 



ELECTRIC TRACTION ON TRUNK LINES. 323 

averaging about loo miles a day for a year, with but one delay 
and that of eight minutes duration. 

When it is remembered that the train detention due to motive 
power troubles expressed in a percentage ratio of the actual 
motive power trouble delay in minutes to total train minutes 
delay from all causes upon an electrified road is but 8.5 per cent, 
and that this small percentage has been materially reduced over 
that of steam service, it may safely be said that present operation 
of electric locomotives is very reliable. 

Increased Capacity of Line. — One of the marked advan- 
tages of electric traction is its large tractive effort for a given size 
and weight of equipment. While this feature is pronounced in 
the electric locomotive because of the elimination of the tender 
and the possible use of such a design as to throw practically all 
the weight of the locomotive upon the drivers, the effect is still 
more marked if motor cars be used, thus making practically the 
entire weight of train available for tractive effort between wheels 
and track. With this relatively great tractive effort, much 
higher rates of acceleration are possible, which in turn permit 
smaller headway between trains and increased traffic capacity 
for a given track. 

This is of particular value upon heavy grades of the single 
track roads of the West, where electrification permits so great 
an increase in traffic over an existing single track that it obviates 
the necessity of double tracking the road for some time to come. 
In this case the cost of electrification may be balanced directly 
against the cost of a second track, which in the mountains of the 
West becomes a formidable figure. 

Further, the length of freight trains using the steam locomotive 
is limited by the strength of the draft gear. With the use of two 
or more electric locomotives at the head of a train, or if the limit 
of the draft gear is reached, possibly the introduction of several 
locomotives throughout the length of the train, all operated by 
means of the multiple unit control from the leading engine will 
probably make possible a greatly increased freight traffic over a 
given road, thus increasing the freight as well as the passenger 
capacity of the line. 

Frequency of Stops. — The ability of the electrically operated 



324 ELECTRIC RAILWAY ENGINEERING. 

train to make more frequent stops and thus better accommodate 
the riding public without reducing the schedule from that of the 
steam road has aheady been explained. 

In addition to the above advantage in some instances it is pos- 
sible to interconnect the local railway system with the electrified 
road in such a way as to transport passengers more nearly to 
their destination without change. 

Both of the above features tend to increase the traffic and 
resulting earnings of the road. 

Convenient Establishment of Feeder Lines. — With the 
reduced cost of power possible with an electrified trunk line, 
short branches of present steam roads or existing suburban or 
interurban lines may be operated electrically much more econom- 
ically than at present. The large and efficient organization of 
the trunk line system also adds materially to this possibility. 
These short branch roads then become valuable feeders to the 
through trunk line. 

Still further economy and convenience to passengers in such 
branch line operation may often be brought about by adding 
branch line motor cars to the through train at junction points, 
operating the entire train thus made up by the multiple unit 
system. 

Improvement of Service. — It is believed that the first question 
to be asked by the directors of a steam road to which reference 
was made early in the chapter has been satisfactorily answered 
by the above improvements in the service, which have been shown 
to be possible upon electrified roads. 

The possibility of increased draw bar pull and more rapid 
acceleration should, however, have more detailed analysis, for it 
is largely with regard to these features that service may be im- 
proved and earnings increased and therefore it is to these features 
to which the present steam railroad officials look at a time when 
service can no longer be increased with present locomotives since 
the latter have practically reached their maximum size and effi- 
ciency. 

DeMuralt has worked out the following table to illustrate the 
relative values of maximum tractive effort available with various 
types of locomotives operating on level track at 60 m. p. h. to 



ELECTRIC TRACTION ON TRUNK LINES. 



o^:) 



which the author has added the last column, which more readily 
compares the locomotives upon a standard basis of unit weight. 
The locomotives selected for this calculation were the New York, 
New Haven and Hartford single-phase and the New York Cen- 
tral direct current locomotives operating in 1907 and a three- 
phase locomotive operated by the Italian State Railways com- 
pared with the most powerful Atlantic and Pacific type steam 
locomotives constructed. 

TABLE XXX. 
Comparison of Electric and Steam Locomotives. 



Max. Tract. 



Wt. of loco- 
motive and 



Max. possible 
Trail, wt. 



Max. T. E. per 
ton wt. of loco- 





etlort Jbs. 


tender tons 


tons 


motive 




Single-phase 


4250 


85 


165 


5c 




Direct current. . . 


6000 


95 


258 


63.2 




Atlantic 


9250 


161 


382 


57-5 




Pacific 


9750 


175 


398 


56.6 




Three-phase 


9375 


95 


457 


98.6 





From the above table it will be seen that the single-phase 
locomotives built at that time had a 13 per cent, lower tractive 
effort and the direct current locomotive a 10 per cent, higher 
effort than the most powerful steam locomotive, while the three- 
phase locomotive was capable of exerting 71.5 per cent, greater 
pull than the latter based upon unit weight of locomotive. 

As values of maximum tractive effort have since been more 
than doubled in the case of the single-phase type and the Pennsyl- 
vania locomotive with its motors above the drivers has been intro- 
duced with a tractive effort 30 per cent, greater than the direct 
current locomotive of the above table, it may be seen that the 
largest steam locomotives are now far excelled in this respect. 

Again, comparing present motor car operation in heavy service 
with that of the steam locomotive it is found that an eight car 
electric train in the New York subway develops a draw bar pull 
more than double the maximum value possible with the largest 
locomotive on the Erie railroad. 

A most inspiring and graphic demonstration of the ability of 



326 ELECTRIC RAILWAY ENGINEERING. 

the New York Central locomotive, particularly in rapid ac 
celeration, was the often quoted test carried out in 1904 on the 
New York. Central Railroad when electric locomotive No. 6000, 
drawing eight Pullman coaches with a total train weigh of 478 . 5 
tons, after reaching the same speed as the New York Central 
fast express was allowed to attain its maximum speed and was 
found to gain a full train length in the distance of one mile. 

Cost of Electrification and Operation. — Granted that the 
service can be improved and the capacity of a road increased 
with electric traction as pointed out above, an answer to the sec- 
ond question must be found, i.e., ''What will it cost to change 
and to operate and maintain the new system when installed?" 

The first cost of the change will vary greatly with local con- 
ditions and in any case would probably be prohibitive if under- 
taken for a complete trunk line system at once. Experimentation, 
if necessary at all, should be carried out upon some of the less 
important branches and the electrical rolling stock secured a 
portion at a time. It has even been suggested that as the pur- 
chase of new steam locomotives to replace those worn out or 
considered obsolete is usually treated by steam roads as an 
operation charge and not a charge against capital, the electrical 
rolling stock, or a large portion of it, might be secured in like 
manner and no great capital investment made for this portion 
of the new system. 

The American Institute of Electrical Engineers was partic- 
ularly fortunate at its 191 1 annual convention to have presented 
by the Pennsylvania Railroad through Mr. B. F. Wood, a very 
detailed statement of the first cost and operating expenses of the 
electrification of the West Jersey and Seashore Railroad. While 
the figures for a larger trunk line operating locomotives in place 
of motor car trains would vary somewhat from those applying 
to this road as illustrated in the discussion which follows, the 
costs of this particular electrification which are the first to be 
made public in complete detail are well worthy of careful study. 
Tables XXXI and XXXII give total and unit costs of electri- 
fication, while operating expenses are well analyzed in Tables 
XXXIII to XXXVI inclusive. The costs apply to a total of 150 
miles of single track upon which 47 to 52 ton cars are operated 



ELECTRIC TRACTION ON TRUNK LINES. 327 

in trains with two 200 h. p. motors per car controlled with the 
multiple unit equipment. The power station is of 8000 k.w. 
capacity supplying power to eight substations ranging from 1000 
to 2500 k.w. each. The distribution voltage on the third rail 
system is 675 volts direct current. 

TABLE XXXI. 1 

Cost of Electrification. 

Power stations: 

Building, stacks, coal and ash handling machinery $354,000 

Equipment 640,900 

Total $994,900 

Transmission line 241,500 

Substations: 

Buildings 72,000 

Equipment 419,560 

Total 491,560 

Third rail 557.636 

Overhead trolley 80,500 

Track bonding 102,659 

Cars 1,135,900 

Car repair and inspection sheds 46,674 

Right-of-way, additional , 592,100 

Reconstructing tracks 763,800 

Constructing new tracks 2,071,000 

Terminal facilities and changes at stations 252,400 

Signals and interlocking plants 561,900 

Changing telegraph and adding telephone facilities 105,100 

Fencing right-of-way, cattle guards, etc 88,400 

Miscellaneous items 44,200 

Total 8,130,229 

TABLE XXXIL^ 

Unit Costs of Electrification. 

Power station, cost per kw $124 .36 

Transmission line, cost per mile 3,485 .00 

Substations, building and equipment cost per kw. ... 28 .90 

Third rail, cost per mile 4,235 .00 

Overhead trolley, cost per mile 4,120 .00 

Track bonding, cost per mile 684 . 50 

Cars, including electrical equipment each 12,214.00 

^"Electrical Operation of the West Jersey and Seashore Railroad," by B. F 
Wood. A. I. E. E. Vol. XXX. 



328 



ELECTRIC RAILWAY ENGINEERING. 



TABLE XXXIII. 1 
Power Station Operation and Maintenance Cost. 



Items 



Year 



Total 



Cent per 
kw-hr. 



.2 
a, 



b 

B 

C/3 



Boiler room 

Turbine 

Labor . -{ Electrical 

I Supervision janitors and watchmen. 

[ Total operating labor 



Material. 



Coal 

Water 

Lubricants 

Misc. material 

Misc. charges 

Total operating material. 
Total operation 



Labor , 



Building 

Boiler room 

Turbine 

Auxiliary apparatus 

Electrical 

Piping 

Miscellaneous 

Total maintenance labor. 



Material. 



Building 

Boiler room 

Turbine 

Auxiliary apparatus 

Electrical 

Piping 

Miscellaneous 

Total maintenance material . 
Total maintenance 



Total labor 

Total material 

Total labor and material station proper . 
Other items charged to station accounts. 

Total 

Net output 

Lbs. coal per kw-hr 

Cost of coal per 2000 lbs 



14,742.36 

10,010.81 

1,661 .02 

2,756 23 



29,170.42 

102,715.31 
500 . 00 



2,238.44 
1,700.49 



107,154.24 



136,324.66 

326 .29 

1,550-44 
836.11 
844.17 

195-30 
691.94 
187.30 



4,631-55 

146.63 

2,493-23 
1,597-52 
2,066 . 13 
3,046.44 

383-97 
599.06 



10,332.98 



14,964.53 

33,801.97 

117,487 .22 

151,289.19 

2,160.60 

153,449-79 
28,312,500 

3.246 

$2,235 



0.052 
0035 
0.006 

O.OIO 



0.103 
0.363 

0.002 



0.007 
0.006 



0.378 



0.481 

O.OOI 

0.005 

0.003 
0.003 

O.OOI 

0.002 

O.OOI 



0.016 

O.OOI 

0.009 
0.006 
0.007 

O.OII 
O.OOI 

0.002 



0.037 



0053 

o. 119 

0.415 
0.534 

0.008 

0.542 



^"Electrical Operation of the West Jersey and Seashore Railroad," by B, F, 
Wood. A. I. E. E. Vol. XXX. 



ELECTRIC TRACTION ON TRUNK LINES. 



329 



TABLE XXXIV. 1 
Cost of Train Oper.\tion per Car Mile. 

















Year 


1909 


















p. 




(U 




l-l 


W) 






Ti 






1 










rt 




t/1 




c 


























0) 




t/l 







CM 
















a 






M 


CI) 






la 






CO 






CO 

<u 
CO 
C 
(U 

a 

0) 




,_l 








c 


-i-> 




V.I 








a; 








oi 






u xn 

■u u 

9, ^ 
<U 

Ij cm 

12 ° 


CO 

w 

a 

03 


a 


a 

a 
■3 




a '^ 

^ CO 




0) 


■> 

u 

(D 
W 


a 


a 

G 
"cS 


"a 

a 

:^ 
CO 


CO 

D 
CO 




lU 

CO ' 

c 
a 

§5 


lies, tot 


u 




"as C 


a 

0) 


OJ 
+-> 







4-> 

4) 


|2 


■4-" 



Clj 

u 


a 


13 
1 


1 


3 1 


a 




Avera 
train 


Avg. . . ■ 


0.68 


1. 10 


0. 


25 


4-3° 


0.33 


0.88 


1.44 


0. 

t 


69 


9.67 


9.08 


18. 75 


\ 4,107,609 


1 
'3-457 



Year 19 10. 



Avg... 0.66 1. 01 0.27 13.33 0.43 0.91 1.52 0.67 



;. 801 9.39 



18.19 I 4.552,532 3-51^ 



TABLE XXXV. ^ 

Cost of Transmission System Mainten.^nce. 



1910. 



/ 


High tension Overhead trolley 


„, . J .. Running track 
Third rail , ,. 

bonding 




Total 


Per ' Total Per Total 
mile mile 

1 i 


Per Total Per 
mile 1 mile 

! 


Total and avg. 
per mi. per mo. 


$3,444.57 


$4- 10 


i 
$4,895-16 $36.70 $10,864.13 


$6.46 '$2,445.72 


$1.36 



TABLE XXXVI. 1 

Cost of substation Operation and Maintenance. 

1910. 



Total for eight substations 



Operation ; Maintenance 



Total 



Cost per 
kw-hr. 



Substation output kw-hr. 
67s volts direct-current 



Year. 



ho, 852. 31 



1,607.30 I $24,459.61 $0.001082 



21,972,300 



^"Electrical Operation of the West Jersey and Seashore Railroad," by B. F 
Wood. A. I. E. E. Vol. XXX. 



330 ELECTRIC RAILWAY ENGINEERING. 

In order to obtain an idea of the magnitude of the cost of electri- 
fication of the trunk lines of the United States, attention should 
be given to the estimates which have been made by Stillwell and 
Putnam/ particularly with regard to the effect upon this cost of 
a reduction of frequency to 15 cycles. Their estimate is based 
upon a continuous output of 2,100,000 k.w. from all the power 
stations combined. The power station apparatus such as tur- 
bines, transformers, meters, etc., which would be effected by 
frequency is estimated at $30 per k.w. at 25 cycles, or $33 at 
15 cycles. Substation transformers would be increased one- 
third in first cost, so that the cost of electrical equipment in 
power house and substations would be increased from $70,000,000 
to $80,000,000, with the decrease in frequency. The assumption 
is made, although open to serious question, that one electric 
locomotive, costing $25,000, will do the work of two de- 
signed for steam operation. With this assumption the aggregate 
cost of electric locomotives will be $600,000,000 at 25 cycles. 
The cost of these locomotives would be reduced with the change 
in frequency by possibly $1,000 each. Storer places this figure 
at $5,000. With the former and more conservative estimate the 
saving with the lower frequency on locomotives, is $24,000,000, 
which is more than double the increase in cost of power station 
and substation equipment. This points toward a conservatively 
estimated saving of $14,000,000 if the lower frequency be chosen. 

Going a step farther into these rather astounding estimates 
the power station equipment for this general electrification figured 
at the low value of $100 per k.w. would amount to $210,- 
000,000, with possibly an added $63,000,000 for substations and 
$600,000,000 for locomotives, etc., reaching a grand total esti- 
mated at one and one-half billions of dollars for the entire under- 
taking. 

Upon the other hand, if the figures quoted by Murray^ based 
upon actual observations of maintenance and operation costs 
upon the electrified section of the New York, New Haven and 

^"On Substitution of the Electric Motor for the Steam Locomotive," by 
Lewis B. Stillwell-and Henry St. Clair Putnam, A. I. E. E. Vol. XXVI. 

^ Discussion by W. S. Murray upon paper, "On the Substitution of the Electric 
Motor for the Steam Locomotive." A. I. E. E. Vol. XXVI. 



ELECTRIC TRACTION ON TRUNK LINES. 



33^ 



Hartford Railroad are given serious consideration, it will be found 
that the above tremendous outlay is not confined to improve- 
ments in service and increased capacity of road alone, but that 
it will return dividends in the form of lowered operating costs and 
maintenance charges as . well. For example. Table XXXVII. 
indicates the saving in coal per annum measured at the power 
house of the electrified system as compared with that used in the 
fire box of the steam locomotive performing the same schedule. 

TABLE XXXVII. 



Ton miles Tons coal 
per annum | steam 
traction 



Tons coal 
electric 
traction 



Cost coal Cost coal | Saving of 
steam ' electric ' elec. over 
traction traction steam 



Express 

Express local. . . 
Express freight. 



592,240,000 

348,000,000 

2,223,000,000 



57.447 

58,300 

187,844 



29,870 

28,600 

139,010 



^183,830 
186,560 
563,530 



$89,620 

85,800 

417,030 



Total saving. 



$94,210 
100,760 
146,500 



$341,470 



This means that the saving in coal alone on a short section of 
but one trunk line will amount to $341,470 per annum due to elec- 
trical operation, while further study of gains in maintenance 
leads to the conclusion that the cost of repairs of the electrical 
equipment will be but one-third or one-fourth that of steam loco- 
motives. These two savings alone when capitalized for all the 
trunk lines of the country will go a great way toward balancing 
the seemingly excessive first cost of electrification estimated above. 

Standardization. — If the prediction made earlier in this dis- 
cussion prove true, and the electrified terminal and tunnel divisions 
of trunk lines gradually expand, as they seem to be expanding 
already, and ultimately they desire to merge together and ex- 
change equipment in order that through service may be main- 
tained over several roads, if one system has selected the 600 volt 
direct current third rail supply as in the case of the New York 
Central, and another the high voltage alternating current trolley 
typical of the New York, New Haven and Hartford, but possibly 
of another frequency and still other mountain divisions expand 
the territory operated with three-phase power, it can readily be 
seen that a situation will result fully as serious as the attempted 



^^2 ELECTRIC RAILWAY ENGINEERING. 

combination not long ago of roads of different track gauges and 
of cars with and without standard air brake equipment. George 
Westinghouse did not sound the warning of standardization any 
too early, therefore, in his recent paper before the London con- 
vention previously alluded to, when he said : 

"For the present it may be a matter of little moment whether 
different systems have their contact conductors in the same 
position, or whether the character of the current used is the same 
or different. As previously stated in the early days of railroading, 
it was of little consequence whether the tracks of the different 
systems in various parts of the country were alike or unlike, but 
later it did make a vital difference, and the variation resulted in 
financial burdens which even yet lie heavily on some railways. 
It is this large view into the future of electrical service which 
should be taken by those responsible for electric railway develop- 
ment." 



INDEX. 



Air brake equipment, 265 
Alternating versus direct current trac- 
tion, 305 

Ballast, 208 

Block signals, 194 

Boilers, 162 

Bonds and bonding, 170 

amalgam, 173 

cast, 173 

compressed terminal, 171 

cross bonding, 177 

soldered and brazed, 171 

testing, 175 

welded, 171 
Brakes, 259 

air brake rigging, 265, 267 

automatic air, 269 

dimensions of brake rigging, 265 

electric, 270 

equipment, 264 

friction disc, 270 

hand brake rigging, 265, 267 

quick action automatic air, 270 

shoes, improper method of hanging, 
264 

shoes, proper method of hanging, 263 

straight air, 267 

track, 270 
Braking (see also brakes), 64 

energy required for, 82 

forces acting during, 262 

friction of brake shoes, 260 

motors used as generators, 271 

reversal of motors, 27 1 

tests, 271 

Cars, city, 226 

elevated and subway, 230 

frames, 220 

gasolene electric, 300 

heating, 223 

lighting, 223 

motor equipment, 221 



Cars, number and capacity, 22 

pay-as-you-enter, 227 

suburban, 229 

trucks, 221 

weight, 48 

wiring, 226 
Car demand curves, 27 
Capacity of transmission line, 14c 
Car house, design, 281 

equipment, 285 

fire protection, 281 

floors, 283 

heating, 283 

lighting, 283 

location, 276 

offices, and employees' quarters, 284 

pit construction, 282 

repair shops, 284 

tracks, 277 

transfer table, 280 
Catenary construction, 100, loi 
Center of gravity of power demands, 105 
Characteristics of motors, 35 

direct current, 35, 39, 40 

single phase, 240 
Charging current of transmission line, 

141 
Chimney, 164 

Coal and ash handling machinery, 165 
Coasting, 63 

energy consumed in, 83 
Competition, relation to traffic of steam 

roads, 19, 21 
Condensers, steam, 159 
Control, alternating current, 256 

combined a. c. d. c, 257 

locomotive, 295 

master, 251 

multiple unit, 252 

rheostatic, 246 

series parallel, 246 

unit switch, 252 

wiring, a. c. d. c, Fig. no 

wiring, multiple unit, 250 



333 



334 



INDEX. 



Control, wiring, series parallel, simpli- 
fied, 248 

wiring, unit switch, multiple unit, 
Fig. 109 

wiring, unit switch, simplified, 254 
Cost, a. c. and d. c. installation, com- 
parative, 314, 315 

a. c. and d. c. operation, compara- 
tive, 315 

electrification, 330 

fuel saved by electrification, 331 

power station, 167, 168, 169 

power station maintenance and 
operation, 150 

power station operation, 328 

roadbed, 218 

substation, 129, 130 

substation, operation and main- 
tenance, 106, 107, 108, 329 

train operation, 329 

transmission system maintenance, 

329 
Current collection, 224 
Current-time curves, 66, 67, 76 
Curves, current-time, 66, 67,- 76 

distance-time, 60, 66, 75 

kilo-volt-ampere-time, 69 

kilowatt- time, 69 

power- time, 68, 76 

resistance due to, 51, 52 

speed-time, 60, 75, 78, 79, 80 

substation load, 89 

track, measurement of, 56 

Distance-time curves, 60, 66, 75 
Distribution, continuous feeder, 92 

division of current between sub- 
stations, 94 

double catenary, loi 

feeder with infrequent taps, 95 

high voltage, direct current, 98 

Kelvin's law, 99 

single-phase, 100 

third rail, 103 

uniformly loaded feeders, 97 
Draft, 164 

Economy, comparison of steam engine 
and turbine, 152 



Electrolysis, 178 

Engine, steam, economy, 152 

specifications, 154 
Energy calculations, 81 

of car, 81 

during breaking period, 82 

during coasting, 83 

Feeders with infrequent taps, 95 

Feed water heaters,' 163 

Feed water pumps, 164 

Frequency, effect of change on motors 

242 
Friction, bearing and rolling, 49 
coefficient for brake shoes, 260 

Gasoline electric car, 300 
Gear ratio, 46 
Grades, 55 

Income, gross, 21 
Induction motor, 242 
Inertia of wheels and armature, rotative, 
52 

Kelvin's Law, 99 
Kilo-volt-ampere-time curves, 69 
Kilowatt-time curves, 69 

Lightning arrester, electrolytic, 125 

Lightning protection, 125 

Load factor, 90 

Locomotives, electric, control systems, 

295 
data, 298, 299 
New York Central, 289 
N. Y. N. H. & H., 290 
Pennsylvania, 296 
Locomotives, steam versus electric, 325 

Motors, adaptation of d. c. series to a. c, 

234 
characteristics, d. c, 35, 39, 40 
characteristics of single-phase, 239 
commutating pole, 233 
direct current, 232 
frequency, effect of change on, 242 
induction, 242 
operation of single phase on d. c, 

240 



INDEX. 



335 



Motors, rating, 242 

repulsion, 241 

selection, 243 

single-phase, 234 

speed curves, 37 

tests, 43 

torque curves, 38 

torque, determination of, 42 

vector diagram of single phase, 235 
Motor equipment, 221 
Motor generator, starting, in 

versus synchronous converter, no 

OfiQces and employees' quarters, 284 

Paving, 214 

Pay-as-you-enter cars, 227 
Population, effect upon traffic, 13 

growth of, 15 
Power demand, center of gravity of, 105 
Power-station, 145 

arrangement of equipment, 166 

boilers, 162 

capacity, 149 

Chicago, Lake Shore & South 
Bend Ry., 148 

chimney, 164 

coal and ash handling machinery, 

165 
condensers, 159 
cost, 167, 168, 169 
design, 147 
double decked, 166 
draft, 164 
elevation of, 151 
elevation of steam turbine, 161 
exciters, 157 
feed water heaters, 163 
feed water pumps, 164 
fuel saving due to electrification, 

location, 145 

maintenance and operation cost, 

150 
operation, 328 
plan of gas engine, 158 
prime movers, 149 
switchboard, 157 
transformers, 156 



Power-time curves, 68, 76 

Rails, 210 

analysis, 212 

corrugation, 214 

joints, 174, 213 
Rail joints, 213 

thermit, 174 

welded, 174 
Rating of motors, 242 
Reactance of transmission line, 136 
Regulation, transmission line, 137 
Repair shops, 284 
Repulsion motor, 241 
Resistance, air, 50 

due to curves, 51, 52 

formula for train, 51 

third rail and track, 93 

train, 83 

transmission line, 136 
Riding habit, 18 
Right of way, 205 
Rolling stock (see cars), 219 

Schedules, train, 30 

Selection of motors, 243 

Signal and despatching systems, 188 

automatic block, 194 

block signals for a. c. roads, 199 

cost, block signals, 201 

double rail a. c. signal, 200 

electric railroad, 197 

lamp signal, 191 

New York subway, 198 

single rail a. c, 197 

steam railroad, 196 

U. S. signal, 192 
Single-phase motors, 234, 239, 240 
Speed-time curves, 60, 75 

straight line, 78 
Standardization of electrified roads, 331 
Standing by preference, 28 
Steam roads, relation of competition to 

traffic of, 19, 21 
Storage battery, auxiliary, 121 
Substation, arrangement of apparatus, 
122 

cost, 129, 130 

demand, 88 



.33^ 



INDEX. 



Substation, design, 109 

division of current between, 94 

financial considerations of, 97 

high voltage, direct current, 127 

lightning protection, 125 

load curve, 89 

location, 104 

operating costs, 106, 107, 108 

operation and maintenance cost, 329 

portable, 126 

single-phase, 128 

switchboard, 117 

typical elevation, 121, 122 

wiring, 123, 124 
Switchboard, power station, 157 

substation, 117 
Synchronous converter, comparative 
ratings, 115 

compounding, 117 

efficiency, 113 

starting, in 

versus motor generator, no 

voltage ratio, 114 

Tests, braking, 271 

motor, prony brake, 27 1 

motor, pumping back, 44 

motor used as generator, 46 

rail bonds, 175 
Thermit rail joints, 174 
Third rail, construction, 102 

distribution, 103 

resistance of, with track, 93 

shoe, 225 
Ties, 208 
Track, ballast, 208 

car house, 277 

construction in Chicago, 185 

curves, measurement of, 56 

estimates, 218 

paving, 214 

rails, 210 

third rail and, resistance of, 93 

ties, 208, 209 

typical construction, 207 
Traction, electric, growth in U. S., 11 
Traction, electric on trunk lines, 319 

alternating versus direct current, 

305 



Traction, electric or trunk lines, 319 
cost, 314, 315, 326 
fuel saving, 331 
locomotives, 325 

operating cost of a. c. and d. c, 315 
power station operation, 328 
standardization, 331 
substation operation and mainte- 
nance cost, 329 
train operation cost, 329 
transmission system, maintenance, 

329 
Tractive effort, consumed in rotating 

parts, 55 
Traffic, effect of population upon, 13 

of steam roads, relation of competi- 
tion to, 20, 21 

statistics, 14 
Train operating costs, 329 
Train schedules, 30 
Transformers, 112 

connections, 115, 116 

power station, 156 

substation, 112 
Transmission line, 131 

capacity, 140 

charging current, 141 

electrical calculations, 134 

maintenance, 329 

mechanical strength, 133 

reactance, 136 

regulation, 137 

resistance, 136 

vector diagram, 138, 139, 142 

voltage determination, 137 
Trucks, 221 

Trunk lines, electric traction upon, 319 
Turbine, steam, economy, 152 

specifications, 153 

Welded rail joints, 174 

Wiring, a. c. d. c. control. Fig. no 

car, 226 

multiple unit, 250 

series parallel, simplified, 248 

substation, 123 

substation diagram, 124 

unit switch, multiple unit, Fig. 109 

unit switch, simplified, 254 



oa m ^9\\ 



'.. A 



One copy del. to Cat. Div. 



OCT rg 1911 



